Switching

---show route---
inet.0: 2409 destinations, 2409 routes (2409 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

 

0.0.0.0/0 *[OSPF/150] 01:12:09, metric 0, tag 0
> to 172.20.100.217 via vlan.2620

72.36.64.0/30 *[OSPF/10] 4d 20:26:01, metric 130
> to 172.20.100.221 via vlan.2621

72.36.64.32/28 *[OSPF/10] 4d 20:26:01, metric 220
> to 172.20.100.217 via vlan.2620

 

This is the ouput of  "show route" . Now lets say we have  a packet with destination 'X' which matches the third rule (highlighted one)  so for this the outgoing interface is a VLAN. 

Is the actual physical interface determined in following way : The router sends a ARP for the nexthop i.e. 172.20.100.217 (from rule 3)  on all physical interfaces which are a part of the VLAN 2621 and then the ARP reply is received from one of the physical interfaces (lets say eth 1/1). then the orignal packet will be send on eth 1/1 ?

 

thanks.

Hello,

Almost there 🙂
Note that the ARP entry is also always tied to the layer-3 interface (which would be a vlan interface in your case). Since the device has a layer-2 domain, the physical interface is actually derived based on which interface is the MAC learned.

In short:
1) Send the ARP for 172.20.100.217.
2) Receive ARP reply, learn it.
3) Check MAC table for the ARP resolution MAC of 172.20.100.217.
4) Send frame out of that physical interface.

HTH

thanks for the confirmation. 

what command can I use  to view a mapping of IP-MAC binding with Outgoing physical interface.

Combination of these commands:

'show arp | match <IP address>' <<<< note MAC-address
'show ethernet-switching table | match <MAC-address>'

Cheers,
ankit

thank you. Should try those out.