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MAC without Port Number.

hanwucisco
Level 1
Level 1

I posted this on LAN/WAN, but it is also rlated to server networking, thanks,

We  have IP device(exchange server, it might be a cluster) on the farm switch(cat6500, which is an access layer  siwtch), with the gateway on the core switches (Nexus7000), on the core  when I do show ip arp, I found the mac

But when I do sh mac add add of that mac there is no port attached to that mac.

Since  that particular vlan only resides on the cat 6500 and two cores, so I  logged in to the 6500, and when I show mac- in that vlan, I didn’t find  that mac addresss. Instead, I found another mac address with last 8bit  are the same of that mac.

Is it some kind VIP of the mac? How so, if no port, how can the switch forward the frame??

Anyone can give some light? I put some show results, hope it is helpful.

By the way, I can ping that IP of the mac.

Thanks,

Han

===========on the core, i did=========

core-2# sh ip arp 10.1.10.6

IP ARP Table

Total number of entries: 1

Address         Age       MAC Address     Interface

10.1.10.6       00:08:44  02bf.0a01.0a06  Vlan906

core-2# sh mac add add 02bf.0a01.0a06

Legend:

        * - primary entry, G - Gateway MAC, (R) - Routed MAC

        age - seconds since last seen,+ - primary entry using vPC Peer-Link

   VLAN     MAC Address      Type      age     Secure NTFY    Ports

---------+-----------------+--------+---------+------+----+------------------

core-2#

==========on the access layer switch, i did=====

SFARM6513-2#sh mac- | i .0a01.0a06

*  906  0202.0a01.0a06   dynamic  Yes          0   Gi4/41

*  906  0201.0a01.0a06   dynamic  Yes          0   Gi9/40

1 Reply 1

jjtanner
Level 1
Level 1

Hi,
I guess your server is doing NLB in unucast mode.
So its correct that you'll never see the MAC learned on any port. Traffic to server is flooded.

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