Routing somewhat like switching?

Unanswered Question
Sep 2nd, 2010
User Badges:

Switches learn which ports connect to which MAC addresses, and direct traffic to them accordingly. 


Is there a routing protocol/config/algorithm which learns which interface connects to a specified subnet by seeing a source IP from that subnet?  And if an IP from the subnet later appears on a different interface, it redirects traffic to that subnet?


Thanks!


Paul

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Loading.
Giuseppe Larosa Thu, 09/02/2010 - 06:50
User Badges:
  • Super Silver, 17500 points or more
  • Hall of Fame,

    Founding Member

Hello Paul,


>> Is there a routing protocol/config/algorithm which learns which interface connects to a specified subnet by seeing a source IP from that subnet?  And if an IP from the subnet later appears on a different interface, it redirects traffic to that subnet?


no as far as I know as a router has to modify packets in order to route ( change TTL and recalculate header checksum and rewrite with appropriate L2 information) and does not simply forward frames between ports.



Hope to help

Giuseppe

Peter Paluch Thu, 09/02/2010 - 07:25
User Badges:
  • Cisco Employee,

Paul, Giuseppe,


There actually is an arcane functionality called IOS Local-Area Mobility which uses ARP packets sent by stations to populate routing tables (!) on routers by host routes towards these stations, essentially allowing a station to freely move throughout the campus. Quite a crude solution but it works. Nevertheless, it is not a protocol, merely a proprietary logic implemented in IOS that uses information contained in ARP messages.


Read more at this URL:


http://www.cisco.com/en/US/products/ps6590/products_white_paper09186a00800a3ca5.shtml


Best regards,

Peter

Giuseppe Larosa Thu, 09/02/2010 - 07:50
User Badges:
  • Super Silver, 17500 points or more
  • Hall of Fame,

    Founding Member

Hello Peter,

we had this in the campus of some works ago and it was used for laptops


I had a vague reminescence but you have found it



Best Regards

Giuseppe

pnicolette Thu, 09/02/2010 - 16:02
User Badges:

Fascinating...thank you, Peter. 


My context (not in the original question!) makes ARP-triggered route changes impractical.  The scenario involves failover between alternate WAN paths which terminate in different organizations.


After some digging, I'm wondering if a closer fit would be Cisco Performance Routing, an enhanced version of Optimized Edge Routing.   A big advantage might be its capacity to reroute traffic based on link degradation as well as complete failure.


Paul

Actions

This Discussion

Related Content