Re: Leaf and Spine topology, route-target / route distinguisher issues

christianpho · ‎12-16-2021

Hi,

I'm trying to understand concept in used in Leaf and Spine topology.

My underlay network is OSPF and all switches has successfull OSPF relationship.

My overlay network is build using eBGP, the 2 SPINES switches are in ASN 64500, and each paire of leaf are in ASN 65000, 65001 and 65002 respectivetly.

My initial intension was to use route-target auto and route distinguiser auto to make the configuration more concise.

I discovere that is not work. I found in the following article, that if the overlay is build with eBGP, the RD and RT has to be defined manually. https://www.cisco.com/c/en/us/products/collateral/switches/nexus-9000-series-switches/guide-c07-734107.html But the article been written in 2018.

Host suppose to belong to the same VNI on different leaf pair, appear in VNI. The host connected on the remote switch do not appear in VNI of the local switch. And it not clear in which VNI is it as the end.

Also, I do not understand why the command "rd 65000:10" on LEAF-1 & 2 to make the VNI 10 working fine if I'm already expecting the routes with the "route-target export 65000:10".

In the current output :

LEAF-1(config-evpn-evi)# sh bgp l2 evpn 
BGP routing table information for VRF default, address family L2VPN EVPN
BGP table version is 950, Local Router ID is 10.0.1.1
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

   Network            Next Hop            Metric     LocPrf     Weight Path
Route Distinguisher: 65000:10
x>e[2]:[0]:[0]:[48]:[5254.0013.b735]:[0]:[0.0.0.0]/216
                      10.0.2.3                                       0 64500 65001 i
x>e[2]:[0]:[0]:[48]:[5254.0013.b735]:[32]:[192.168.1.2]/248
                      10.0.2.3                                       0 64500 65001 i
x>e[3]:[0]:[32]:[10.0.2.3]/88
                      10.0.2.3                                       0 64500 65001 i

Route Distinguisher: 65001:30
x>e[2]:[0]:[0]:[48]:[5254.0006.8b57]:[0]:[0.0.0.0]/216
                      10.0.2.5                                       0 64500 65002 i
x>e[3]:[0]:[32]:[10.0.2.5]/88
                      10.0.2.5                                       0 64500 65002 i

Route Distinguisher: 10.0.1.1:32777    (L2VNI 10)
*>l[2]:[0]:[0]:[48]:[5254.000d.0334]:[0]:[0.0.0.0]/216
                      10.0.2.1                          100      32768 i
*>l[2]:[0]:[0]:[48]:[5254.000d.0334]:[32]:[192.168.1.1]/248
                      10.0.2.1                          100      32768 i
*>l[3]:[0]:[32]:[10.0.2.1]/88
                      10.0.2.1                          100      32768 i

I understand that the host 192.168.1.2 is learn with route distinguiser 65000:10, but it is connected to LEAF-3 which is in ASN 65001, with the "rd auto" actually configured the route distinguisher should be 65001:10 instead.

Now, I know the RT and RD are announced to BGP neighbor using extended community. Using route-map is any way that I can say if route-target is 65001:10 import it in 65000:10, 650001:20 in 65000:20 and so on ?

In case, I can used "rd auto" and "route-taget export auto" in combination of the route-map command for the "route-taget import" part, making my evpn configuration much smaller.

I attached the configuration of each router, connectivity diagram in the PDF file, and the yaml file of the setup in CML 2.2.6.

In the topology :

machine_1vlan10 is configured with 1921.168.1.1/24 GW 192.168.1.254

machine_2vlan10 is configured with 1921.168.1.2/24 GW 192.168.1.254

machine_1vlan30 is configured with 1921.168.2.1/24 GW 192.168.2.254

machine_2vlan30 is configured with 1921.168.2.2/24 GW 192.168.2.254

MHM Cisco World · ‎12-17-2021

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