Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

AD ON STATIC ROUTES

I have a small question about floating static routes, how does the route know when the next hop has gone down and to use the next route with higher AD ? does it use some simple icmp checks ?

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: AD ON STATIC ROUTES

Hello Carl,

without object tracking the router will consider  the IP next-hop reachable until the interface where the IP subnet of the next-hop is up.

In case of LAN switched environment, the L3 interface can be an SVI and the next-hop can die without L3 interface to fail too.

In this case the next-hop is considered valid until the associated ARP entry is valid up to 4 hours on a cisco device with default settings.

In a LAN environment : or move to dynamic routing or you need to use reliable static routing

see

http://www.cisco.com/en/US/docs/ios/12_3/12_3x/12_3xe/feature/guide/dbackupx.html

the primary static route next-hop has to be tracked using an tracking object or an IP SLA (IOS version dependent)

when the tracked object / IP SLA fails the primary route is removed from IP routing table and secondary route (with higher AD) is installed.

Hope to help

Giuseppe

1 REPLY
Hall of Fame Super Silver

Re: AD ON STATIC ROUTES

Hello Carl,

without object tracking the router will consider  the IP next-hop reachable until the interface where the IP subnet of the next-hop is up.

In case of LAN switched environment, the L3 interface can be an SVI and the next-hop can die without L3 interface to fail too.

In this case the next-hop is considered valid until the associated ARP entry is valid up to 4 hours on a cisco device with default settings.

In a LAN environment : or move to dynamic routing or you need to use reliable static routing

see

http://www.cisco.com/en/US/docs/ios/12_3/12_3x/12_3xe/feature/guide/dbackupx.html

the primary static route next-hop has to be tracked using an tracking object or an IP SLA (IOS version dependent)

when the tracked object / IP SLA fails the primary route is removed from IP routing table and secondary route (with higher AD) is installed.

Hope to help

Giuseppe

154
Views
0
Helpful
1
Replies