blog/2024/asymmetric-routing-with-sr-linux-in-evpn-vxlan-fabrics/

[giscus[bot]]

blog/2024/asymmetric-routing-with-sr-linux-in-evpn-vxlan-fabrics/

Open documentation for open Network OS

https://asymmetric-evpnvxlan.learn-srlinux.pages.dev/blog/2024/asymmetric-routing-with-sr-linux-in-evpn-vxlan-fabrics/

[hasanashik]

Why there is not ip-vrf configured for inter vlan routing? How two irb subinterface will talk each other without ip vrf?

[aninchat]

I'm not sure if I understand the question correctly, but IP VRFs are not a necessity for inter-VLAN routing or asymmetric routing in EVPN VXLAN fabrics.

[tonybourke]

I see mostly symmetric IRB these days, what would be a reason one might choose asymmetric over symmetric?

[aninchat-nokia]

I agree, I think symmetric IRB is generally the preferred option in most cases. For asymmetric, the reasons are not as compelling but they could be - smaller scale fabric with low ARP/MAC scale and thus, consistent BD/IRB configuration across all VTEPs (easier to operate and maintain when using orchestrators or automation tools like Ansible). Blog (and a nokia validated design for symmetric IRB) will come in a few months.

[amp109]

Shouldn't the IRB interface be associated with an IP VRF?

A:leaf1# show network-instance macvrf1 interfaces

Net instance : macvrf1
Interface : irb0.10
Oper state : down
Oper down reason: ip-vrf-association-missing

[aninchat-nokia]

Do you have the IRB interface mapped to either an IP VRF or default network-instance? Please paste the MAC VRF and default or IP VRF network-instance configuration.

[amp109]

Thank you for your reply.
I tried to create the configuration from the article. So I need to associate the IRB with an IP-VRF or the default instance, correct?

info network-instance macvrf1
network-instance macvrf1 {
type mac-vrf
admin-state enable
interface ethernet-1/3.0 {
}
interface irb0.10 {
}
vxlan-interface vxlan1.1 {
}
protocols {
bgp-evpn {
bgp-instance 1 {
admin-state enable
vxlan-interface vxlan1.1
evi 10
ecmp 2
}
}
bgp-vpn {
bgp-instance 1 {
route-distinguisher {
rd 192.0.2.11:1
}
route-target {
export-rt target:10:10
import-rt target:10:10
}
}
}
}
}

info network-instance default
network-instance default {
interface ethernet-1/1.0 {
}
interface ethernet-1/2.0 {
}
interface system0.0 {
}
protocols {
bgp {
admin-state enable
autonomous-system 65411
router-id 192.0.2.11
afi-safi evpn {
admin-state enable
}
afi-safi ipv4-unicast {
admin-state enable
multipath {
maximum-paths 2
}
}
group spine {
peer-as 65500
export-policy [
spine-export
]
import-policy [
spine-import
]
afi-safi evpn {
admin-state enable
}
afi-safi ipv4-unicast {
admin-state enable
}
}
neighbor 198.51.100.1 {
peer-group spine
}
neighbor 198.51.100.3 {
peer-group spine
}
}
}
}

[aninchat-nokia]

Yes, the IRB interface must belong to a network-instance - either the default network-instance or an IP VRF network-instance. For asymmetric, it does not matter much since it works even with default network-instance (unless you want to provide L3 isolation, in which case, place it in an IP VRF network-instance).