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EVPN table look up

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  • 1.  EVPN table look up

    Posted 12-24-2020 13:12

    Hi everybody,

    Please consider following simple EVPN set up:

    HOST1 ------------MX1------Cloud-----MX4---HOST2

    MX1 and MX2 are PE with EVPN instance defined.

     #HOST1##

    MAC:aa:aa:aa;aa:aa:aa

    IP: 100.100.100.1/24

     #HOST2##

    MAC:22.22.22.22.22.22

    IP: 100.100.100.2/24

    MX4 has following EVPN table:

    root@MX4> show route table EVPN-1.evpn.0

    2:1.1.1.1:1::0::aa:aa:aa:aa:aa:aa/304 MAC/IP
    *[BGP/170] 00:00:41, localpref 100, from 2.2.2.2
    AS path: I, validation-state: unverified
    > to 24.24.24.2 via ge-0/0/0.0, Push 18

    2:1.1.1.1:1::0::aa:aa:aa:aa:aa:aa::100.100.100.1/304 MAC/IP
    *[BGP/170] 00:00:41, localpref 100, from 2.2.2.2
    AS path: I, validation-state: unverified
    > to 24.24.24.2 via ge-0/0/0.0, Push 18

    So we have two routes, one is MAC , the other one is MAC+IP for host1.

    Let say host 2  ( 100.100.100.2)  sends ping to 100.100.100.1 with destination mac: aa:aa:aa:aa:aa:aa

    Which  entry will MX4 use to forward this packet?  is it   2:1.1.1.1:1::0::aa:aa:aa:aa:aa:aa/304 MAC/IP or

    2:1.1.1.1:1::0::aa:aa:aa:aa:aa:aa::100.100.100.1/304 MAC/IP ?

    Thanks in advance!!



  • 2.  RE: EVPN table look up
    Best Answer

    Posted 12-25-2020 01:18

    In Type 2 routes, I understand that the IP address portion is optional and set to zero (like we see in one of your routes)

    During data transmissions, a host knows the IP Address to communicate with, either manually or via DNS, and MAC address resolution needs to occur, which is the purpose of the Type 2 route... to advertise the MAC address.

    In the case of the IP address being provided, (shown in your other Type 2 route) I understand that this is used in a proxy-arp scenario for arp suppression.

    So I think the answer to your question is, in most typical cases, this one is used.

    2:1.1.1.1:1::0::aa:aa:aa:aa:aa:aa/304 MAC/IP



    ------------------------------
    Aaron Gould
    Senior Network Engineer
    aaron@gvtc.com
    https://www.linkedin.com/in/agould123/
    ------------------------------