Example: Configuring MPLS over GRE with IPsec Fragmentation and Reassembly
This example is based on a need to support a standard 1,500 byte MTU to virtual private network (VPN) clients that are supported by GRE over IPsec tunnels, when the WAN provider does not offer a Jumbo MTU option. The traffic forwarded over the 1500-byte WAN link can be dropped because the protocol encapsulation overhead (Layer 2, MPLS, GRE and IPsec) results in a frame that exceeds the WAN link MTU.
MTU related drops are mostly an issue for traffic that cannot be fragmented. For example, IP traffic that is marked as do-not-fragment, or Layer 2 VPN/VPLS traffic, which by its nature, cannot be fragmented. For performance reasons, many IPsec configurations block post encryption fragmentation, resulting in packet drop.
This document provide a solution to this problem by showing you how to configure an IPsec tunnel to perform post-fragmentation on traffic that is otherwise not able to be fragmented. In this case you trade encryption performance by forcing post-fragmentation against having to reduce the MTU of your VPN clients to prevent MTU related drops.
This example shows how to configure selective packet services mode using a single routing instance (the default one) to process VPN traffic into packet mode. In packet mode security zones are bypassed. This means that the Layer 2 and Layer 3 VRF interfaces are not placed into a security zone and no policy is needed to allow them to communicate through the internet zone.
Using the steps in this example you can perform IPsec encapsulated packet fragmentation on the outgoing physical interface of the sending device and reassembly on the receiving device before IPsec decryption.
The reassembly of fragmented packets uses a lot of device resources, and the performance of the device will be slower than with nonfragmented traffic. When possible you should configure a jumbo MTU on the WAN interface to avoid the need for fragmentation. This example shows you how to provide a standard 1,500 byte MTU to client devices that block fragmentation when using IPsec over a WAN connection that does not offer jumbo support.
The topic includes the following sections:
Requirements
This example uses the following hardware and software components:
Two SRX Series Services Gateways
Junos OS Release 11.4 or later
This example has been revalidated on Junos OS Release 20.3R1
For this example to work as documented you must ensure
that your SRX configuration does not have any interfaces with family ethernet-switching enabled. Using family ethernet-switching puts the SRX device into mixed mode operation. This example is based
on the route mode of operation. For details on route and mixed modes
of operation see Understanding Layer 2 Interfaces on Security Devices. In addition,
we tested this example with the factory default settings for the edit protocols l2-learning hierarchy.
Overview and Topology
This example includes the following configurations:
Configure interfaces for the appropriate protocol encapsulation and maximum transmission unit (MTU) value.
Apply firewall filter on the ge-0/0/0.10 interface to set the packet mode. Configure the WAN facing interface ge-0/0/1.0 with a 1,524 byte MTU.
Set a large MTU value to GRE and IPsec logical interfaces to avoid IPsec fragmentation at logical interfaces. The GRE encapsulated traffic is tunneled inside IPsec.
Add the MPLS family to the GRE interface gr-0/0/0, and apply firewall filters to enable packet mode.
Configure an IPsec tunnel on the device with the
df-bit clearoption in the IPsec VPN configuration to allow fragmentation of oversized IPsec packets on the outgoing ge-0/0/1.0 interface. This setting allows the SRX device to perform fragmentation post IPsec encryption for VPN client traffic that is marked with the do not fragment (DNF) bit. VPN client traffic that is not marked as DNF is fragmented prior to IPsec encryption to improve performance.Configure all noncustomer- facing interfaces such as ge-0/0/1.0, gr-0/0/0.0, lo0.0, and st0.0 in a single security zone called “Internet”. A single security zone is used in this example to keep the focus on fragmentation issues with MPLS over GRE over IPSec. Security can be enhanced by placing the device into flow-mode for MPLS, and then placing the customer-facing interfaces into a zone. Once in a zone, security policies can control communications, and evoke advanced features like IDP and application recognition. For more information see Security Zones.
Configure a policy to permit all (intrazone) traffic.
Configure OSPF for lo0.0 address distribution, LDP for label distribution/MPLS transport, and IBGP with the
inet-vpnandl2vpnfamilies to support the VPN clients.Configure two routing instances, one for a Layer 3 VPN and one for a Layer 2 VPLS service.
Figure 1 shows the topology for this example.
This example focuses on VPLS and a Layer 3 VPN over an IPsec tunnel. Layer 2 Circuits are also supported. For a Layer 2 circuit you need to configure both a family MPLS filter and a family CCC filter. The filters are used to evoke packet mode processing in order to support fragmentation over IPsec.
Topology
Table 1 provides a summary of the parameters used in this topology for the PE1 device. You can adapt the parameters for the PE2 device, or use the PE2 quick configuration provided below.
Components |
Description |
|---|---|
PE1 |
PE1 SRX Series Firewall: ge-0/0/0.10:
|
ge-0/0/2.11:
|
|
ge-0/0/1.0:
|
|
gr-0/0/0:
|
|
lo0:
|
|
st0.0:
|
|
|
Configuration
Procedure
CLI Quick Configuration
To quickly configure this example, copy the
following commands, paste them into a text file, remove any line breaks,
change any details necessary to match your network configuration,
copy and paste the commands into the CLI at the [edit] hierarchy
level, and then enter commit from configuration mode.
The configuration for the SRX1 (PE1) device:
set system host-name SRX1 set security ike policy standard mode main set security ike policy standard proposal-set standard set security ike policy standard pre-shared-key ascii-text "$9$1OsIclKvL7NblegoGUHk" set security ike gateway srx-2 ike-policy standard set security ike gateway srx-2 address 172.16.23.1 set security ike gateway srx-2 external-interface ge-0/0/1.0 set security ipsec policy standard proposal-set standard set security ipsec vpn ipsec-vpn-1 bind-interface st0.0 set security ipsec vpn ipsec-vpn-1 df-bit clear set security ipsec vpn ipsec-vpn-1 ike gateway srx-2 set security ipsec vpn ipsec-vpn-1 ike ipsec-policy standard set security ipsec vpn ipsec-vpn-1 establish-tunnels immediately set security policies from-zone Internet to-zone Internet policy Internet match source-address any set security policies from-zone Internet to-zone Internet policy Internet match destination-address any set security policies from-zone Internet to-zone Internet policy Internet match application any set security policies from-zone Internet to-zone Internet policy Internet then permit set security zones security-zone Internet host-inbound-traffic system-services all set security zones security-zone Internet host-inbound-traffic protocols all set security zones security-zone Internet interfaces ge-0/0/1.0 set security zones security-zone Internet interfaces gr-0/0/0.0 set security zones security-zone Internet interfaces lo0.0 set security zones security-zone Internet interfaces st0.0 set interfaces ge-0/0/0 vlan-tagging set interfaces ge-0/0/0 mtu 4000 set interfaces ge-0/0/0 description L3VPN set interfaces ge-0/0/0 unit 10 vlan-id 10 set interfaces ge-0/0/0 unit 10 family inet filter input packet-mode-inet set interfaces ge-0/0/0 unit 10 family inet address 192.168.0.1/24 set interfaces gr-0/0/0 description "MPLS core facing interface" set interfaces gr-0/0/0 unit 0 tunnel source 172.16.0.1 set interfaces gr-0/0/0 unit 0 tunnel destination 172.16.0.2 set interfaces gr-0/0/0 unit 0 family inet mtu 9000 set interfaces gr-0/0/0 unit 0 family inet address 172.16.255.1/30 set interfaces gr-0/0/0 unit 0 family mpls mtu 9000 set interfaces gr-0/0/0 unit 0 family mpls filter input packet-mode set interfaces ge-0/0/1 description Internet set interfaces ge-0/0/1 mtu 1514 set interfaces ge-0/0/1 unit 0 family inet address 172.16.13.1/30 set interfaces ge-0/0/2 flexible-vlan-tagging set interfaces ge-0/0/2 mtu 1522 set interfaces ge-0/0/2 encapsulation vlan-vpls set interfaces ge-0/0/2 unit 11 description VPLS set interfaces ge-0/0/2 unit 11 encapsulation vlan-vpls set interfaces ge-0/0/2 unit 11 vlan-id 512 set interfaces lo0 unit 0 family inet address 10.255.255.1/32 set interfaces st0 unit 0 family inet mtu 9178 set interfaces st0 unit 0 family inet address 172.16.0.1/30 set firewall family inet filter packet-mode-inet term all-traffic then packet-mode set firewall family inet filter packet-mode-inet term all-traffic then accept set firewall family mpls filter packet-mode term all-traffic then packet-mode set firewall family mpls filter packet-mode term all-traffic then accept set routing-instances L3VPN routing-options auto-export set routing-instances L3VPN interface ge-0/0/0.10 set routing-instances L3VPN instance-type vrf set routing-instances L3VPN route-distinguisher 10.255.255.1:1000 set routing-instances L3VPN vrf-target target:65100:1000 set routing-instances L3VPN vrf-table-label set routing-instances VPLS protocols vpls site 1 interface ge-0/0/2.11 set routing-instances VPLS protocols vpls site 1 site-identifier 1 set routing-instances VPLS protocols vpls no-tunnel-services set routing-instances VPLS protocols vpls mac-tlv-receive set routing-instances VPLS protocols vpls mac-tlv-send set routing-instances VPLS interface ge-0/0/2.11 set routing-instances VPLS instance-type vpls set routing-instances VPLS route-distinguisher 10.255.255.1:1001 set routing-instances VPLS vrf-target target:65100:1001 set protocols ospf traffic-engineering set protocols ospf area 0.0.0.0 interface lo0.0 passive set protocols ospf area 0.0.0.0 interface gr-0/0/0.0 set protocols bgp group IBGP type internal set protocols bgp group IBGP local-address 10.255.255.1 set protocols bgp group IBGP local-as 65100 set protocols bgp group IBGP neighbor 10.255.255.2 family inet any set protocols bgp group IBGP neighbor 10.255.255.2 family inet-vpn any set protocols bgp group IBGP neighbor 10.255.255.2 family l2vpn signaling set protocols bgp tcp-mss 1200 set protocols ldp interface gr-0/0/0.0 set protocols ldp interface lo0.0 set protocols mpls interface gr-0/0/0.0 set routing-options static route 172.16.23.0/30 next-hop 172.16.13.2 set routing-options router-id 10.255.255.1
The configuration for the SRX2 (PE2) device:
set system host-name SRX2 set security ike policy standard mode main set security ike policy standard proposal-set standard set security ike policy standard pre-shared-key ascii-text "$9$Ahg6tORhclvMXREdb2gJZ" set security ike gateway srx-1 ike-policy standard set security ike gateway srx-1 address 172.16.13.1 set security ike gateway srx-1 external-interface ge-0/0/1.0 set security ipsec policy standard proposal-set standard set security ipsec vpn ipsec-vpn-1 bind-interface st0.0 set security ipsec vpn ipsec-vpn-1 df-bit clear set security ipsec vpn ipsec-vpn-1 ike gateway srx-1 set security ipsec vpn ipsec-vpn-1 ike ipsec-policy standard set security ipsec vpn ipsec-vpn-1 establish-tunnels immediately set security policies from-zone Internet to-zone Internet policy Internet match source-address any set security policies from-zone Internet to-zone Internet policy Internet match destination-address any set security policies from-zone Internet to-zone Internet policy Internet match application any set security policies from-zone Internet to-zone Internet policy Internet then permit set security zones security-zone Internet host-inbound-traffic system-services all set security zones security-zone Internet host-inbound-traffic protocols all set security zones security-zone Internet interfaces ge-0/0/1.0 set security zones security-zone Internet interfaces gr-0/0/0.0 set security zones security-zone Internet interfaces lo0.0 set security zones security-zone Internet interfaces st0.0 set interfaces ge-0/0/0 vlan-tagging set interfaces ge-0/0/0 mtu 4000 set interfaces ge-0/0/0 description L3VPN set interfaces ge-0/0/0 unit 10 vlan-id 10 set interfaces ge-0/0/0 unit 10 family inet filter input packet-mode-inet set interfaces ge-0/0/0 unit 10 family inet address 192.168.1.1/24 set interfaces gr-0/0/0 description "MPLS core facing interface" set interfaces gr-0/0/0 unit 0 tunnel source 172.16.0.2 set interfaces gr-0/0/0 unit 0 tunnel destination 172.16.0.1 set interfaces gr-0/0/0 unit 0 family inet mtu 9000 set interfaces gr-0/0/0 unit 0 family inet address 172.16.255.2/30 set interfaces gr-0/0/0 unit 0 family mpls mtu 9000 set interfaces gr-0/0/0 unit 0 family mpls filter input packet-mode set interfaces ge-0/0/1 description Internet set interfaces ge-0/0/1 mtu 1514 set interfaces ge-0/0/1 unit 0 family inet address 172.16.23.1/30 set interfaces ge-0/0/2 flexible-vlan-tagging set interfaces ge-0/0/2 mtu 1522 set interfaces ge-0/0/2 encapsulation vlan-vpls set interfaces ge-0/0/2 unit 11 description VPLS set interfaces ge-0/0/2 unit 11 encapsulation vlan-vpls set interfaces ge-0/0/2 unit 11 vlan-id 512 set interfaces lo0 unit 0 family inet address 10.255.255.2/32 set interfaces st0 unit 0 family inet mtu 9178 set interfaces st0 unit 0 family inet address 172.16.0.2/30 set firewall family inet filter packet-mode-inet term all-traffic then packet-mode set firewall family inet filter packet-mode-inet term all-traffic then accept set firewall family mpls filter packet-mode term all-traffic then packet-mode set firewall family mpls filter packet-mode term all-traffic then accept set routing-instances L3VPN routing-options auto-export set routing-instances L3VPN interface ge-0/0/0.10 set routing-instances L3VPN instance-type vrf set routing-instances L3VPN route-distinguisher 10.255.255.2:1000 set routing-instances L3VPN vrf-target target:65100:1000 set routing-instances L3VPN vrf-table-label set routing-instances VPLS protocols vpls site 2 interface ge-0/0/2.11 set routing-instances VPLS protocols vpls site 2 site-identifier 2 set routing-instances VPLS protocols vpls no-tunnel-services set routing-instances VPLS protocols vpls mac-tlv-receive set routing-instances VPLS protocols vpls mac-tlv-send set routing-instances VPLS interface ge-0/0/2.11 set routing-instances VPLS instance-type vpls set routing-instances VPLS route-distinguisher 10.255.255.2:1001 set routing-instances VPLS vrf-target target:65100:1001 set protocols ospf traffic-engineering set protocols ospf area 0.0.0.0 interface lo0.0 passive set protocols ospf area 0.0.0.0 interface gr-0/0/0.0 set protocols bgp group IBGP type internal set protocols bgp group IBGP local-address 10.255.255.2 set protocols bgp group IBGP local-as 65100 set protocols bgp group IBGP neighbor 10.255.255.1 family inet any set protocols bgp group IBGP neighbor 10.255.255.1 family inet-vpn any set protocols bgp group IBGP neighbor 10.255.255.1 family l2vpn signaling set protocols bgp tcp-mss 1200 set protocols ldp interface gr-0/0/0.0 set protocols ldp interface lo0.0 set protocols mpls interface gr-0/0/0.0 set routing-options static route 172.16.13.0/30 next-hop 172.16.23.2 set routing-options router-id 10.255.255.2
Step-by-Step Procedure
The following example requires you to navigate various levels in the configuration hierarchy. For instructions on how to do that, see Using the CLI Editor in Configuration Mode in the CLI User Guide for Junos OS.
To fragment the MPLS frame and reassemble the packet:
Configure the physical Interfaces.
[edit interfaces] user@SRX1# set ge-0/0/0 description L3VPN user@SRX1# set ge-0/0/0 mtu 4000 user@SRX1# set ge-0/0/0 unit 10 vlan-id 10 user@SRX1# set ge-0/0/0 unit 10 family inet filter input packet-mode-inet user@SRX1# set ge-0/0/0 unit 10 family inet address 192.168.0.1/24 user@SRX1# set ge-0/0/1 description Internet user@SRX1# set ge-0/0/1 mtu 1514 user@SRX1# set ge-0/0/1 unit 0 family inet address 172.16.13.1/30 user@SRX1# set ge-0/0/2 description VPLS user@SRX1# set ge-0/0/2 flexible-vlan-tagging user@SRX1# set ge-0/0/2 mtu 1522 user@SRX1# set ge-0/0/2 encapsulation vlan-vpls user@SRX1# set ge-0/0/2 unit 11 encapsulation vlan-vpls user@SRX1# set ge-0/0/2 unit 11 vlan-id 512
Configure the logical Interfaces.
[edit interfaces] user@SRX1# set gr-0/0/0 unit 0 description "MPLS core facing interface" user@SRX1# set gr-0/0/0 unit 0 tunnel source 172.16.0.1 user@SRX1# set gr-0/0/0 unit 0 tunnel destination 172.16.0.2 user@SRX1# set gr-0/0/0 unit 0 family inet mtu 9000 user@SRX1# set gr-0/0/0 unit 0 family inet address 172.16.255.1/30 user@SRX1# set gr-0/0/0 unit 0 family mpls mtu 9000 user@SRX1# set gr-0/0/0 unit 0 family mpls filter input packet-mode user@SRX1# set lo0 unit 0 family inet address 10.255.255.1/32 user@SRX1# set st0 unit 0 family inet mtu 9178 user@SRX1# set st0 unit 0 family inet address 172.16.0.1/30
Configure the firewall filters that are used to configure interfaces to work with packet mode.
[edit firewall] user@SRX1# set family inet filter packet-mode-inet term all-traffic then packet-mode user@SRX1# set family inet filter packet-mode-inet term all-traffic then accept user@SRX1# set family mpls filter packet-mode term all-traffic then packet-mode user@SRX1# set family mpls filter packet-mode term all-traffic then accept
Note:If you are configuring a Layer 2 Circuit you must also add a filter to evoke packet mode on the CE-facing interface under family CCC:
set firewall family ccc filter packet-mode-ccc term all-traffic then packet-mode set firewall family ccc filter packet-mode-ccc term all-traffic then accept
Configure the IKE and IPsec policies.
[edit security] user@SRX1# set ike policy standard mode main user@SRX1# set ike policy standard proposal-set standard user@SRX1# set ike policy standard pre-shared-key ascii-text "$9$1OsIclKvL7NblegoGUHk" user@SRX1# set ike gateway srx-2 ike-policy standard user@SRX1# set ike gateway srx-2 address 172.16.23.1 user@SRX1# set ike gateway srx-2 external-interface ge-0/0/1.0 user@SRX1# set ipsec policy standard proposal-set standard user@SRX1# set ipsec vpn ipsec-vpn-1 bind-interface st0.0 user@SRX1# set ipsec vpn ipsec-vpn-1 df-bit clear user@SRX1# set ipsec vpn ipsec-vpn-1 ike gateway srx-2 user@SRX1# set ipsec vpn ipsec-vpn-1 ike ipsec-policy standard user@SRX1# set ipsec vpn ipsec-vpn-1 establish-tunnels immediately
Note:To keep the focus on fragmentation over IPsec we use the default cypher in this example (3DES-CBC). For increased performance and security consider using a newer cypher, such as AES-GCM-256. see encryption-algorithm (Security IKE)
Configure all noncustomer-facing interfaces in a single security zone and a policy to permit all (intrazone) traffic.
[edit security policies from-zone Internet to-zone Internet] user@SRX1# set policy Internet match source-address any user@SRX1# set policy Internet match destination-address any user@SRX1# set policy Internet match application any user@SRX1# set policy Internet then permit [edit security zones security-zone Internet] user@SRX1# set host-inbound-traffic system-services all user@SRX1# set host-inbound-traffic protocols all user@SRX1# set interfaces ge-0/0/1.0 user@SRX1# set interfaces gr-0/0/0.0 user@SRX1# set interfaces lo0.0 user@SRX1# set interfaces st0.0
Configure the OSPF protocol for lo0.0 address distribution, configure IBGP with the inet-vpn and l2vpn families. Also configure MPLS and LDP signaling.
[edit protocols] user@SRX1# set bgp tcp-mss 1200 user@SRX1# set bgp group IBGP type internal user@SRX1# set bgp group IBGP local-address 10.255.255.1 user@SRX1# set bgp group IBGP local-as 65100 user@SRX1# set bgp group IBGP neighbor 10.255.255.2 user@SRX1# set bgp group IBGP neighbor 10.255.255.2 family inet any user@SRX1# set bgp group IBGP neighbor 10.255.255.2 family inet-vpn any user@SRX1# set bgp group IBGP neighbor 10.255.255.2 family l2vpn signaling user@SRX1# set ospf traffic-engineering user@SRX1# set ospf area 0.0.0.0 interface lo0.0 user@SRX1# set ospf area 0.0.0.0 interface lo0.0 passive user@SRX1# set ospf area 0.0.0.0 interface gr-0/0/0.0 user@SRX1# set mpls interface gr-0/0/0.0 user@SRX1# set ldp interface gr-0/0/0.0 user@SRX1# set ldp interface lo0.0
Configure the router ID and a static route to the remote end of the WAN link.
[edit routing-option] user@SRX1# set static route 172.16.23.0/30 next-hop 172.16.13.2 user@SRX1# set router-id 10.255.255.1
Configure two routing instances, one for Layer 3 VPN and the other for the VPLS application.
[edit routing-instances] user@SRX1# set L3VPN instance-type vrf user@SRX1# set L3VPN route-distinguisher 10.255.255.1:1000 user@SRX1# set L3VPN interface ge-0/0/0.10 user@SRX1# set L3VPN vrf-target target:65100:1000 user@SRX1# set L3VPN vrf-target import target:65100:1000 user@SRX1# set L3VPN vrf-target export target:65100:1000 user@SRX1# set L3VPN vrf-table-label user@SRX1# set L3VPN routing-options auto-export user@SRX1# set VPLS instance-type vpls user@SRX1# set VPLS interface ge-0/0/2.11 user@SRX1# set VPLS route-distinguisher 10.255.255.1:1001 user@SRX1# set VPLS vrf-target target:65100:1001 user@SRX1# set VPLS protocols vpls no-tunnel-services user@SRX1# set VPLS protocols vpls site 1 site-identifier 1 user@SRX1# set VPLS protocols vpls site 1 interface ge-0/0/2.11 user@SRX1# set VPLS protocols vpls mac-tlv-receive user@SRX1# set VPLS protocols vpls mac-tlv-send
Results
Display the results of the configuration:
user@SRX1> show configuration
security {
ike {
policy standard {
mode main;
proposal-set standard;
pre-shared-key ascii-text "$9$1OsIclKvL7NblegoGUHk"; ## SECRET-DATA
}
gateway srx-2 {
ike-policy standard;
address 172.16.23.1;
external-interface ge-0/0/1.0;
}
}
ipsec {
policy standard {
proposal-set standard;
}
vpn ipsec-vpn-1 {
bind-interface st0.0;
df-bit clear;
ike {
gateway srx-2;
ipsec-policy standard;
}
establish-tunnels immediately;
}
}
policies {
from-zone Internet to-zone Internet {
policy Internet {
match {
source-address any;
destination-address any;
application any;
}
then {
permit;
}
}
}
}
zones {
security-zone Internet {
host-inbound-traffic {
system-services {
all;
}
protocols {
all;
}
}
interfaces {
ge-0/0/1.0;
gr-0/0/0.0;
lo0.0;
st0.0;
}
}
}
}
interfaces {
ge-0/0/0 {
vlan-tagging;
mtu 4000;
unit 10 {
description L3VPN;
vlan-id 10;
family inet {
filter {
input packet-mode-inet;
}
address 192.168.0.1/24;
}
}
}
gr-0/0/0 {
unit 0 {
description "MPLS core facing interface";
tunnel {
source 172.16.0.1;
destination 172.16.0.2;
}
family inet {
mtu 9000;
address 172.16.255.1/30;
}
family mpls {
mtu 9000;
filter {
input packet-mode;
}
}
}
}
ge-0/0/1 {
description Internet;
mtu 1514;
unit 0 {
family inet {
address 172.16.13.1/30;
}
}
}
ge-0/0/2 {
flexible-vlan-tagging;
mtu 1522;
encapsulation vlan-vpls;
unit 11 {
description VPLS;
encapsulation vlan-vpls;
vlan-id 512;
}
}
lo0 {
unit 0 {
family inet {
address 10.255.255.1/32;
}
}
}
st0 {
unit 0 {
family inet {
mtu 9178;
address 172.16.0.1/30;
}
}
}
}
firewall {
family inet {
filter packet-mode-inet {
term all-traffic {
then {
packet-mode;
accept;
}
}
}
}
family mpls {
filter packet-mode {
term all-traffic {
then {
packet-mode;
accept;
}
}
}
}
}
routing-instances {
L3VPN {
routing-options {
auto-export;
}
interface ge-0/0/0.10;
instance-type vrf;
route-distinguisher 10.255.255.1:1000;
vrf-target {
target:65100:1000;
import target:65100:1000;
export target:65100:1000;
}
vrf-table-label;
}
VPLS {
protocols {
vpls {
site 1 {
interface ge-0/0/2.11;
site-identifier 1;
}
no-tunnel-services;
mac-tlv-receive;
mac-tlv-send;
}
}
interface ge-0/0/2.11;
instance-type vpls;
route-distinguisher 10.255.255.1:1001;
vrf-target target:65100:1001;
}
}
protocols {
ospf {
traffic-engineering;
area 0.0.0.0 {
interface lo0.0 {
passive;
}
interface gr-0/0/0.0;
}
}
bgp {
group IBGP {
type internal;
local-address 10.255.255.1;
local-as 65100;
neighbor 10.255.255.2 {
family inet {
any;
}
family inet-vpn {
any;
}
family l2vpn {
signaling;
}
}
}
tcp-mss 1200;
}
ldp {
interface gr-0/0/0.0;
interface lo0.0;
}
mpls {
interface gr-0/0/0.0;
}
}
routing-options {
static {
route 172.16.23.0/30 next-hop 172.16.13.2;
}
router-id 10.255.255.1;
}
Verification
Confirm that the configuration is working properly.
- Verifying That the Physical and Logical Interfaces Are Up
- Verifying IPsec Security Associations
- Verifying OSPF and BGP
- Verifying LDP Operation
- Verifying The VPLS Connection
- Verifying End-to-End VPLS Connectivity for Large Packets with DNF Set
- Verifying IP Fragmentation on the Outgoing Interface
- Verifying The L3VPN
Verifying That the Physical and Logical Interfaces Are Up
Purpose
Verify that the physical and logical interfaces are up on the device.
Action
From operational mode on the SRX Series Services Gateway,
enter the show interfaces terse command.
user@SRX1> show interfaces terse
Interface Admin Link Proto Local Remote
ge-0/0/0 up up
ge-0/0/0.10 up up inet 192.168.0.1/24
ge-0/0/0.32767 up up
gr-0/0/0 up up
gr-0/0/0.0 up up inet 172.16.255.1/30
mpls
ip-0/0/0 up up
lsq-0/0/0 up up
lt-0/0/0 up up
mt-0/0/0 up up
sp-0/0/0 up up
sp-0/0/0.0 up up inet
inet6
sp-0/0/0.16383 up up inet
ge-0/0/1 up up
ge-0/0/1.0 up up inet 172.16.13.1/30
ge-0/0/2 up up
ge-0/0/2.11 up up vpls
ge-0/0/2.32767 up up
dsc up up
fti0 up up
fxp0 up up
fxp0.0 up up inet 10.54.5.56/19
gre up up
ipip up up
irb up up
lo0 up up
lo0.0 up up inet 10.255.255.1 --> 0/0
lo0.16384 up up inet 127.0.0.1 --> 0/0
lo0.16385 up up inet 10.0.0.1 --> 0/0
10.0.0.16 --> 0/0
128.0.0.1 --> 0/0
128.0.0.4 --> 0/0
128.0.1.16 --> 0/0
lo0.32768 up up
lsi up up
lsi.0 up up inet
iso
inet6
lsi.1048576 up up vpls
. . .
<some output removed for brevity>Meaning
The output of the show interfaces terse command
shows that all physical and logical interfaces used in this configuration
are operational.
Verifying IPsec Security Associations
Purpose
Verify that the IKE and IPsec security associations are up on the device.
Action
From operational mode on the SRX Series Services Gateway,
enter the show security ike security-association and show security ipsec security-association commands.
user@SRX1>show security ike security-associationsIndex State Initiator cookie Responder cookie Mode Remote Address 6699112 UP 2a5d1a37e5bd0cd1 09880f53cdbb35bb Main 172.16.23.1 user@SRX1>show security ipsec security-associationsTotal active tunnels: 1 Total Ipsec sas: 1 ID Algorithm SPI Life:sec/kb Mon lsys Port Gateway <131073 ESP:3des/sha1 f1396d7e 1868/ unlim - root 500 172.16.23.1 >131073 ESP:3des/sha1 ff799c04 1868/ unlim - root 500 172.16.23.1
Meaning
The output shows the expected Up state for the IKE session and that an IPsec tunnel is successfully established.
Verifying OSPF and BGP
Purpose
Verify that OSPF and BGP are operating correctly over the GRE tunnel. Recall that the GRE tunnel is in turn routed over the IPsec tunnel verified in the previous step. Proper OSPF/BGP operation in this example indirectly verifies that traffic is able to pass over the GRE (and then the IPsec) tunnel. If desired, you can ping the GRE endpoint for added verification.
Action
From operational mode on the SRX Series Services Gateway,
enter the show ospf neighbor and show bgp summary commands.
user@SRX1>show ospf neighborAddress Interface State ID Pri Dead 172.16.255.2 gr-0/0/0.0 Full 10.255.255.2 128 33 user@SRX1>show bgp summaryThreading mode: BGP I/O Default eBGP mode: advertise - accept, receive - accept Groups: 1 Peers: 1 Down peers: 0 Table Tot Paths Act Paths Suppressed History Damp State Pending inet.0 0 0 0 0 0 0 inet.2 0 0 0 0 0 0 bgp.l3vpn.0 1 1 0 0 0 0 bgp.l3vpn.2 0 0 0 0 0 0 bgp.l2vpn.0 1 1 0 0 0 0 Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped... 10.255.255.2 65100 988 988 0 1 7:21:03 Establ inet.0: 0/0/0/0 inet.2: 0/0/0/0 bgp.l3vpn.0: 1/1/1/0 bgp.l3vpn.2: 0/0/0/0 bgp.l2vpn.0: 1/1/1/0 L3VPN.inet.0: 1/1/1/0 VPLS.l2vpn.0: 1/1/1/0
Meaning
The output confirms the expected OSPF neighbor state
of full. This OSPF neighbor is estanlished over the GRE
interface. Given OSPF is operational, you expect that the local SRX
has learned the route to the remote SRX’s loopback address.
This route allows the loopback based IBGP peering session to establish
(over the GRE tunnel). The output of the show bgp summary command confirms the BGP session is in the established state, and
that it is exchanging both L3VPN and L2VPN routes.
Verifying LDP Operation
Purpose
Verify that LDP is operating correctly over the GRE tunnel. LDP functions as the MPLS signaling protocol in this example.
Action
From operational mode on the SRX Series Services Gateway,
enter the show ldp neighbor and show ldp session commands.
user@SRX1>show ldp neighborAddress Interface Label space ID Hold time 172.16.255.2 gr-0/0/0.0 10.255.255.2:0 12 user@SRX1>show ldp sessionAddress State Connection Hold time Adv. Mode 10.255.255.2 Operational Open 28 DU
Meaning
The output confirms the expected LDP neighbor relationship
over the GRE interface. The output of the show ldp session command confirms successful session establishment to the remote
SRX device’s loopback address. This allows LDP to exchange transport
labels that in turn support MPLS forwarding for the VPN clients.
Verifying The VPLS Connection
Purpose
Verify that the VPLS connection is in an up state.
Action
From operational mode on the SRX Series Services Gateway,
enter the show vpls connections command.
user@SRX1> show vpls connections
Layer-2 VPN connections:
Legend for connection status (St)
EI -- encapsulation invalid NC -- interface encapsulation not CCC/TCC/VPLS
EM -- encapsulation mismatch WE -- interface and instance encaps not same
VC-Dn -- Virtual circuit down NP -- interface hardware not present
CM -- control-word mismatch -> -- only outbound connection is up
CN -- circuit not provisioned <- -- only inbound connection is up
OR -- out of range Up -- operational
OL -- no outgoing label Dn -- down
LD -- local site signaled down CF -- call admission control failure
RD -- remote site signaled down SC -- local and remote site ID collision
LN -- local site not designated LM -- local site ID not minimum designated
RN -- remote site not designated RM -- remote site ID not minimum designated
XX -- unknown connection status IL -- no incoming label
MM -- MTU mismatch MI -- Mesh-Group ID not available
BK -- Backup connection ST -- Standby connection
PF -- Profile parse failure PB -- Profile busy
RS -- remote site standby SN -- Static Neighbor
LB -- Local site not best-site RB -- Remote site not best-site
VM -- VLAN ID mismatch HS -- Hot-standby Connection
Legend for interface status
Up -- operational
Dn -- down
Instance: VPLS
Edge protection: Not-Primary
Local site: 1 (1)
connection-site Type St Time last up # Up trans
2 rmt Up Aug 25 07:52:38 2021 1
Remote PE: 10.255.255.2, Negotiated control-word: No
Incoming label: 262146, Outgoing label: 262145
Local interface: lsi.1048578, Status: Up, Encapsulation: VPLS
Description: Intf - vpls VPLS local site 1 remote site 2
Flow Label Transmit: No, Flow Label Receive: NoMeaning
The output shows the expected Up state for
the VPLS connection. With the connection operational, the VPN client
devices should be able to pass traffic.
Verifying End-to-End VPLS Connectivity for Large Packets with DNF Set
Purpose
Verify that the Layer 2 VPLS client devices are able to send 1500 byte frames with the DNF bit set. Because this is a Layer 2 service, fragmentation is not possible. As a result the DNF bit operates end-to-end. Recall that with the configuration in this example, such a setting results in the ingress SRX device fragmenting the IPsec packet after the traffic has been encrypted (post-fragmentation). The post-fragmentation occurs as the traffic egresses the WAN facing ge-0/0/1 interface.
Post-fragmentation forces the remote SRX device to reassemble
the packet before it can perform decryption, which can impact forwarding
performance for encrypted traffic. This is the expected behavior when
the df-bit clear option is used. Demonstration this behavior
is the reason for this NCE. The other df-bit options, namely df-bit copy and df-bit set, result in packet discard
and generation of an ICMP error message for VPN packets that exceed
the WAN MTU when the DNF bit is set by the VPN client.
Action
From operational mode on VPLS Host1, ping VPLS Host2
in a manner that generates a 1500 byte IP packet with the DNF bit
set. When this traffic has the MPLS, GRE, and IPsec overhead added
it exceeds the outgoing WAN interface’s MTU. Given that pre-fragmentation
is blocked by virtue of this being a Layer 2 service (or in the case
of the L3VPN client, by setting the DNF bit), such a packet forces
post-fragmentation based on the setting of the df-bit clear option
The configuration and operation of the VPN client devices are outside the scope of this example. For testing, a MX router is used to act as the VPN clients. As a result the ping command demonstrated is based on the Junos CLI.
user@vpls-host1> ping 192.168.2.102 size 1472 do-not-fragment count 2
PING 192.168.2.102 (192.168.2.102): 1472 data bytes
1480 bytes from 192.168.2.102: icmp_seq=0 ttl=64 time=23.045 ms
1480 bytes from 192.168.2.102: icmp_seq=1 ttl=64 time=5.342 ms
--- 192.168.2.102 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 5.342/14.194/23.045/8.852 msMeaning
The output shows the pings succeed. The 1480 bytes of echo traffic results in a 1500 byte IP packet when the 20 byte IP header is added. Thus, the results confirm the VPLS client device can exchange 1,500 byte packets over a WAN link with a 1,500 byte MTU, despite the encapsulation overhead. Recall that because this is a Layer 2 service, fragmentation is not possible and the DNF bit operates end-to-end. Using the DNF bit is significant when testing the L3VPN client, however, because the PE device is able to fragment IP traffic.
Verifying IP Fragmentation on the Outgoing Interface
Purpose
Verify that VPLS client traffic that exceeds the WAN MTU is fragmented on the outgoing ge-0/0/1.0 interface. Timing is important in this step because background OSPF, LDP, and BGP traffic causes the ge-0/0/0.0 interface counters to increment. The goal is to generate 100 1,500 byte packets from the VPLS host and then quickly compare the IPsec and interface statistics to confirm that approximately twice as many packets are seen on the outgoing WAN interface when compared to the counts on the IPsec tunnel.
Action
From operational mode on the SRX Series Services Gateway,
clear both the IPsec and interface statistics with the clear
interfaces statistics all and clear security ipsec statistics commands. Then generate 100 rapid pings with a 1,500 byte packet
size between the VPLS endpoints. When the pings complete, display
packet counts for the IPsec tunnel and the ge-0/0/1 interface with
the show interfaces ge-0/0/1 detail and show security
ipsec statistics commands.
user@SRX1>clear interfaces statistics alluser@SRX1>clear interfaces statistics all
Generate 100 rapid pings with a packet size of 1,500 bytes between the VPLS endpoints. This is not shown for brevity. Refer to the command in the previous step. Not shown here for brevity.
user@SRX1>show interfaces ge-0/0/1 detailPhysical interface: ge-0/0/1, Enabled, Physical link is Up Interface index: 136, SNMP ifIndex: 509, Generation: 139 Description: Internet Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Link-mode: Full-duplex, Speed: 10Gbps, BPDU Error: None, Loop Detect PDU Error: None, Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Enabled Device flags : Present Running Interface flags: SNMP-Traps Internal: 0x4000 Link flags : None CoS queues : 8 supported, 8 maximum usable queues Hold-times : Up 0 ms, Down 0 ms Current address: 56:04:19:00:3a:7b, Hardware address: 56:04:19:00:3a:7b Last flapped : 2021-08-27 12:17:01 PDT (01:27:43 ago) Statistics last cleared: 2021-08-27 13:44:28 PDT (00:00:16 ago) Traffic statistics: Input bytes : 163440 0 bps Output bytes : 162000 0 bps Input packets: 210 0 pps Output packets: 200 0 pps Egress queues: 8 supported, 4 in use . . . user@SRX1>show security ipsec statisticsESP Statistics: Encrypted bytes: 161896 Decrypted bytes: 155722 Encrypted packets: 113 Decrypted packets: 112 . . .
Meaning
The output of the show interfaces ge-0/0/1.0 detail command shows that over200 packets have been sent and received.
In contrast, the IPsec statistics confirm a count of around 100 packets.
This confirms that each packet sent by the VPLS client was fragmented
on the WAN-facing ge-0/0/1.0 interface.
Verifying The L3VPN
Purpose
Verify L3VPN Operation.
Action
From operational mode on the SRX Series Services Gateway,
display the route to the remote L3VPN subnet with the show route command. Then generate pings to the remote L3VPN endpoint to verify
connectivity.
user@SRX1> show route 192.168.1.0/24
L3VPN.inet.0: 3 destinations, 3 routes (3 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
192.168.1.0/24 *[BGP/170] 01:05:44, localpref 100, from 10.255.255.2
AS path: I, validation-state: unverified
> via gr-0/0/0.0, Push 16
bgp.l3vpn.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
10.255.255.2:1000:192.168.1.0/24
*[BGP/170] 01:05:44, localpref 100, from 10.255.255.2
AS path: I, validation-state: unverified
> via gr-0/0/0.0, Push 16Test connectivity from the local SRX to the remote VPN endpoint:
user@SRX1> ping 192.168.1.101 routing-instance L3VPN count 2
PING 192.168.1.101 (192.168.1.101): 56 data bytes
64 bytes from 192.168.1.101: icmp_seq=0 ttl=63 time=3.485 ms
64 bytes from 192.168.1.101: icmp_seq=1 ttl=63 time=3.412 ms
--- 192.168.1.101 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 3.412/3.449/3.485/0.036 ms
In this configuration a ping from the local SRX to the local L3VPN client does not succeed. This relates to the use of packet mode and the lack of security zones for the VPN interfaces. As shown above, you are able to ping from the local SRX to the remote L3VPN destinations. Though not shown, a ping generated from the local L3VPN client to the local PE VRF interface is expected to succeed.
Test end-to-end connectivity for the L3VPN. Generate jumbo pings between L3VPN client endpoints. Recall that the L3VPN client is configured with a 4k MTU in this example. Once again we use a MX router to fill in for the L3VPN client, so Junos ping syntax is used:
user@l3vpn1> ping 192.168.1.101 size 3000 do-not-fragment count 2
PING 192.168.1.101 (192.168.1.101): 3000 data bytes
3008 bytes from 192.168.1.101: icmp_seq=0 ttl=62 time=5.354 ms
3008 bytes from 192.168.1.101: icmp_seq=1 ttl=62 time=5.607 ms
--- 192.168.1.101 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 5.354/5.481/5.607/0.126 msMeaning
The output shows the route to the remote L3VPN client is correctly learned via BGP, and that it points to the GRE interface with an MPLS label operation. The results from ping testing confirm expected connectivity for the L3VPN even when sending 3,000 + byte pings with the DNF bit set.