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[MX] Example - Mapping an EVPN instance to choose a different LSP path for forwarding

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Article ID: KB35493 KB Last Updated: 28 Feb 2020Version: 1.0 Summary:

This article explains how users can map EVPN instances to choose different label-switched paths (LSPs) as the forwarding path with the help of an example.

 

Symptoms:

Topology

In the above topology, R1, R2, R3, and R4 are the core routers. R5 and R6 are the customer end devices. Here, we have defined two Ethernet VPN (EVPN) instances on R1 and R4 as evpna and evpnb, respectively.

  • R1-R2=10.1.1.0/30

  • R2-R3=10.1.1.4/30

  • R3-R4=10.1.1.8/30

  • R4-R1=10.1.1.12/30

Two Resource Reservation Protocol (RSVP) LSPs are created on the core routers as below:

  • Path_Direct_R4 = Strict hop to R4

  • Path_Indirect_R4 = Strict hop to R4 via R2 and R3

For instance, if customer wants evpna instance traffic to be sent via the existing LSP Path_Direct_R4 and evpnb instance traffic to be sent via Path_Indirect_R4, the following configuration would be used: 
set routing-options route-distinguisher-id 1.1.1.1
set routing-instances evpna description "to Path_Direct_R4"
set routing-instances evpna instance-type evpn
set routing-instances evpna vlan-id 3057
set routing-instances evpna interface ge-0/0/3.3057
set routing-instances evpna vrf-target target:1:1
set routing-instances evpna protocols evpn interface ge-0/0/3.3057

set routing-instances evpnb description "Path_Indirect_R4"
set routing-instances evpnb instance-type evpn
set routing-instances evpnb vlan-id 707
set routing-instances evpnb interface ge-0/0/4.707
set routing-instances evpnb vrf-target target:1:2
set routing-instances evpnb protocols evpn interface ge-0/0/4.707

Using a similar configuration as above, evpn is configured on the R4 router as well for instances evpna and evpnb.

However, when we check the forwarding table for each evpn instance, it shows two LSP paths as next-hop, because the default behavior is to show multiple next-hops.

lab@R1_re# run show route forwarding-table vpn evpna.0       
Routing table: evpna.evpn
EVPN:
Enabled protocols: Single VLAN, ACKed by all peers, EVPN, ARP/NDP suppression,
Destination        Type RtRef Next hop           Type Index    NhRef Netif
default            perm     0                    dscd      608     1
56:68:a5:d1:11:ca/48 user     0                 chain 15695870     2
56:68:a5:d1:11:d2/48 user     0                  ucst      613     4 ge-0/0/3.3057
0x30005/51         user     0                    comp      659     2
ge-0/0/3.3057      intf     0                    ucst      613     4 ge-0/0/3.3057
0x30004/51         user     0                    comp      635     2
0x30002/51         user     0                    comp      632     2
                   intf     0                    indr  1048577     3
                                                 ulst  1048576     2
                              10.1.1.13     Push 299808      639     2 ge-0/0/2.181
                              10.1.1.2      Push 299808, Push 300080(top)      640     2 ae3.0
lab@R1_re# run show route forwarding-table vpn evpnb.0
Routing table: evpnb.evpn
EVPN:
Enabled protocols: Single VLAN, ACKed by all peers, EVPN, ARP/NDP suppression,
Destination        Type RtRef Next hop           Type Index    NhRef Netif
default            perm     0                    dscd      604     1
56:68:a5:d1:11:cb/48 user     0                 chain 15695871     2
56:68:a5:d1:20:54/48 user     0                  ucst      612     4 ge-0/0/4.707
0x30006/51         user     0                    comp      662     2
ge-0/0/4.707       intf     0                    ucst      612     4 ge-0/0/4.707
0x30003/51         user     0                    comp      626     2
0x30001/51         user     0                    comp      623     2
                   intf     0                    indr  1048579     3
                                                 ulst  1048578     2
                              10.1.1.13     Push 299776      643     2 ge-0/0/2.181
                              10.1.1.2      Push 299776, Push 300080(top)      645     2 ae3.0

 

Solution:

To configure an instance to choose a specific LSP as the next-hop, use the following example:

  1. Configure the following policy to map the instance to a different LSP as the next-hop:

set policy-options policy-statement evpn_map_lsp term evpna from rib mpls.0
set policy-options policy-statement evpn_map_lsp term evpna from community evpna
set policy-options policy-statement evpn_map_lsp term evpna then install-nexthop lsp Path_Direct_R4
set policy-options policy-statement evpn_map_lsp term evpna then accept

set policy-options policy-statement evpn_map_lsp term evpnb from rib mpls.0
set policy-options policy-statement evpn_map_lsp term evpnb from community evpnb
set policy-options policy-statement evpn_map_lsp term evpnb then install-nexthop lsp Path_Indirect_R4
set policy-options policy-statement evpn_map_lsp term evpnb then accept

  1. Define the community:

set policy-options community evpna members target:1:1
set policy-options community evpnb members target:1:2

  1. Apply the policy:

set routing-options forwarding-table export evpn_map_lsp
--

lab@R1_re# run show route forwarding-table vpn evpna   
Routing table: evpna.evpn
EVPN:
Enabled protocols: Single VLAN, ACKed by all peers, EVPN, ARP/NDP suppression,
Destination        Type RtRef Next hop           Type Index    NhRef Netif
default            perm     0                    dscd      608     1
56:68:a5:d1:11:ca/48 user     0                 chain 15695870     2
56:68:a5:d1:11:d2/48 user     0                  ucst      613     4 ge-0/0/3.3057
0x30005/51         user     0                    comp      659     2
ge-0/0/3.3057      intf     0                    ucst      613     4 ge-0/0/3.3057
0x30004/51         user     0                    comp      635     2
0x30002/51         user     0                    comp      632     2
                   intf     0                    indr  1048580     3
                              10.1.1.13     Push 299808      643     2 ge-0/0/2.181
 
[edit]
lab@R1_re# run show route forwarding-table vpn evpnb   
Routing table: evpnb.evpn
EVPN:
Enabled protocols: Single VLAN, ACKed by all peers, EVPN, ARP/NDP suppression,
Destination        Type RtRef Next hop           Type Index    NhRef Netif
default            perm     0                    dscd      604     1
56:68:a5:d1:11:cb/48 user     0                 chain 15695871     2
56:68:a5:d1:20:54/48 user     0                  ucst      612     4 ge-0/0/4.707
0x30006/51         user     0                    comp      662     2
ge-0/0/4.707       intf     0                    ucst      612     4 ge-0/0/4.707
0x30003/51         user     0                    comp      626     2
0x30001/51         user     0                    comp      623     2
                   intf     0                    indr  1048581     3
                              10.1.1.2      Push 299776, Push 300080(top)      640     2 ae3.0

Verification

  1. Initiate a ping from instance evpna CPE IP to CPE IP at the other end.

lab@R5_re# run ping 192.168.10.2 source 192.168.10.1 rapid count 100   
PING 192.168.10.2 (192.168.10.2): 56 data bytes
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
--- 192.168.10.2 ping statistics ---
100 packets transmitted, 100 packets received, 0% packet loss
round-trip min/avg/max/stddev = 3.916/13.068/149.216/20.133 ms
 
lab@R1_re# run show mpls lsp statistics ingress name Path_* | refresh 2
---(refreshed at 2020-02-15 09:22:56 PST)---
Ingress LSP: 2 sessions
To              From            State     Packets            Bytes LSPname
4.4.4.4    1.1.1.1   Up              0                0 Path_Direct_R4
4.4.4.4    1.1.1.1   Up              0                0 Path_Indirect_R4
Total 2 displayed, Up 2, Down 0
---(refreshed at 2020-02-15 09:22:58 PST)---
Ingress LSP: 2 sessions
To              From            State     Packets            Bytes LSPname
4.4.4.4    1.1.1.1   Up            100            10200 Path_Direct_R4 >>>> Forwarding path is chosen as LSP Path_Direct_R4 and packets are incrementing.
4.4.4.4    1.1.1.1   Up              0                0 Path_Indirect_R4
Total 2 displayed, Up 2, Down 0

  1. Similarly, initiate a ping from instance evpnb CPE IP to CPE IP at the other end:

lab@R5_re# run ping 192.168.20.2 source 192.168.20.1 rapid count 100   
PING 192.168.20.2 (192.168.20.2): 56 data bytes
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
--- 192.168.20.2 ping statistics ---
100 packets transmitted, 100 packets received, 0% packet loss
round-trip min/avg/max/stddev = 5.003/31.223/181.715/40.707 ms
 
lab@R1_re# run show mpls lsp statistics ingress name Path_* | refresh 2   
---(refreshed at 2020-02-15 09:24:38 PST)---
Ingress LSP: 2 sessions
To              From            State     Packets            Bytes LSPname
4.4.4.4    1.1.1.1   Up            100            10200 Path_Direct_R4
4.4.4.4    1.1.1.1   Up              0                0 Path_Indirect_R4
Total 2 displayed, Up 2, Down 0
---(refreshed at 2020-02-15 09:24:40 PST)---
Ingress LSP: 2 sessions
To              From            State     Packets            Bytes LSPname
4.4.4.4    1.1.1.1   Up            100            10200 Path_Direct_R4
4.4.4.4    1.1.1.1   Up             84             8568 Path_Indirect_R4
Total 2 displayed, Up 2, Down 0
---(refreshed at 2020-02-15 09:24:42 PST)---
Ingress LSP: 2 sessions
To              From            State     Packets            Bytes LSPname
4.4.4.4    1.1.1.1   Up            100            10200 Path_Direct_R4
4.4.4.4    1.1.1.1   Up            100            10200 Path_Indirect_R4 >>>> Forwarding path is chosen as LSP Path_Indirect_R4 and packets are incrementing.
Total 2 displayed, Up 2, Down 0

 

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