Posted on November 16, 2021 1:54 pm
 |  Asked by Daniil Kharun
 |  81 views
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To conserve IP address space, we use unnumbered interfaces.
We use the 192.0.2.0/24 network for our customers, the address 192.0.2.1 is used as a gateway.

Configuration example:

interface Loopback3
vrf internet
ip address 192.0.2.1/32
ip route vrf internet 192.0.2.250/32 Vlan100
ip route vrf internet 192.0.2.251/32 Vlan101
ip route vrf internet 192.0.2.252/32 Vlan102
interface Vlan100
vrf internet
ip proxy-arp
ip address unnumbered Loopback3
interface Vlan101
vrf internet
ip proxy-arp
ip address unnumbered Loopback3
interface Vlan102
vrf internet
ip proxy-arp
ip address unnumbered Loopback3

But how to apply unnumbered interfaces for active-active router configuration with MLAG? I cannot use the gateway address as a virtual-router address:

(config-if-Vl100)#ip virtual-router address 192.0.2.1
% Address 192.0.2.1 is already assigned to interface Loopback3

0
Answered on November 17, 2021 5:57 am

Hi Daniil Kharun,

Thanks for reaching out.

As of now we can't assign/configure unnumbered interface feature for ip virtual-router address / ip virtual address commands(Anycast GW). When configuring VARP using "ip virtual-router address" we need to assign an ip address for each SVI(Physical IP for SVI Vlan) +Virtual IP address for VIP (Anycast GW) and they should be different. However when configuring "ip virtual address" we can use only 1 ip under SVI i.e Virtual IP and it doesn't require an IP address to be assigned to the SVI interface(i.e no need to assign Physical IP for SVI ).

We don't have the option to configure the unnumbered command feature under CLI as it hasn't been implemented as of now:

switch(config-if-Vl10)#ip virtual-router address ?
A.B.C.D IP address
A.B.C.D/E IP prefix address

switch(config-if-Vl10)#ip address virtual ?
A.B.C.D IP address
A.B.C.D/E IP address with mask length

 

Please find the following TOI for Ipv4 Unnumbered interfaces feature:

https://eos.arista.com/eos-4-23-0f/ipv4-unnumbered-interfaces

 

Thanks,

Bhavana.

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