Floating Static route

[MITCH JOHNSON]

If I have two ways to the internet and one goes down, is the only way to send users out to the internet through a floating static route? Such that,

ip route 0.0.0.0 0.0.0.0 10.10.10.1

ip route 0.0.0.0 0.0.0.0 10.200.10.1 100, where the 100 allows the static default route to be replaced when the primary route is down? How would the router know when a static route is down?

[pkhatri]

Hi,

What you have suggested is certainly one way of doing it ? The trick is to ensure that your primary static route does go down when your link breaks. With links such as ethernet links, the physical interface may remain up although the connection itself is broken. In such cases, you need to use a reliable static route backup option where you use track objects to track reachability through the link.

However, if what you have is a couple of serial links, the idea of using floating static routes will work perfectly well.

The other alternative is to run BGP with your provider.

Hope that helps - pls rate the post if it does.

Paresh

[jarathbu]

Hello,

If your primary default route should always reachable via a particular interface you can include that in the static route statement - so if that interface goes down - your floating static will be effective.

Hope that helps.

Regards,

James

[MITCH JOHNSON]

Thanks for the input. As usual I left key information out of the question, such as the ethernet interface part. I can't use BGP as neither ISP is willing to do BGP. I guess what I'm asking is how to make ethernet interfaces know when a neighbor isn't reachable. It's not very often that an ethernet interface goes down, it's usually a serial interface further down the line that goes down, then I usually go in manualy to change the default route.

Once again, thankyou.

[pkhatri · Accepted solution]

Hi,

If you are running a relatively new IOS (12.3(8)T, I believe) you can use the reliable static route backup feature. This feature allows you to detect failures downstream from your ethernet connection.

Here's a sample config:

Replace with an IP that you can ping through your main link - preferably the ISP side of the WAN link address.

interface Ethernet 0

description Main Link

ip address 10.1.1.1 255.0.0.0

!

interface Ethernet 1

description Backup Link

ip address 192.168.1.1 255.0.0.0

!

ip sla monitor 1

type echo protocol ipIcmpEcho

timeout 1000

frequency 3

threshold 2

!

ip sla monitor schedule 1 life forever start-time now

!

track 100 rtr 1 reachability

!

access list 101 permit icmp any host echo

!

route-map LOCAL_POLICY permit 10

match ip address 101

set ip next-hop 10.1.1.254

set interface null0

!

ip local policy route-map LOCAL_POLICY

!

ip route 0.0.0.0 0.0.0.0 10.1.1.254 track 100

ip route 0.0.0.0 0.0.0.0 192.168.1.254 254

Hope that helps - pls do rate the post if it does.

Paresh

[tin.ngo]

Paresh, is there a link where your example comes from explaining what each command does?

I am considering implementing the above with Serial as primary path and ethernet as secondary path with IPsec (over Internet). Just need to understand it a bit more.

[pkhatri]

Here is the link:

http://www.cisco.com/en/US/products/sw/iosswrel/ps5413/products_feature_guide09186a00801d862d.html

Pls do remember to rate posts.

Paresh

[tin.ngo]

IOS 12.3(14)T I beleived replace "rtr" with "ip sla" command. Do you have a link with sample configuration similar to the above (i.e primary and backup link) using ip sla command instead?

If not, can you convert the above using ip sla? Thanks.

[pkhatri]

Here's a config I use - you will need to adjust it for your requirements;

Replace with an IP that you can ping through your main link - preferably the ISP side of the WAN link address.

interface Ethernet 0

description Main Link

ip address 10.1.1.1 255.0.0.0

!

interface Ethernet 1

description Backup Link

ip address 192.168.1.1 255.0.0.0

!

ip sla monitor 1

type echo protocol ipIcmpEcho

timeout 1000

frequency 3

threshold 2

!

ip sla monitor schedule 1 life forever start-time now

!

track 100 rtr 1 reachability

!

access list 101 permit icmp any host echo

!

route-map LOCAL_POLICY permit 10

match ip address 101

set ip next-hop 10.1.1.254

set interface null0

!

ip local policy route-map LOCAL_POLICY

!

ip route 0.0.0.0 0.0.0.0 10.1.1.254 track 100

ip route 0.0.0.0 0.0.0.0 192.168.1.254 254

Pls do remember to rate posts.

Paresh

[guruprasadr]

Hi Paresh,

I am a Guruprasad.R working as Network Administrator in Saksoft Ltd for the past 6 months. I am a new guy to the Networking world.I finished my B.Tech[Information Technology] by May 2005.

I finished my CCNA by Jan 06 and i am currently focussing on CCNP(BCMSN) paper. I used to visit discussion forums frequently. I was supposed to see that all questions were replied by you.

I am really proud of you. I have more idea and interest in the Security Environment. So, Kindly guide me in my career. Expecting you guidance, kindness and wishes to make my career the best one.

Your's Truly,

Guruprasad.R

Mail id: itguruprasad@yahoo.com