Tracking routes and distributing through the OSPF

[blwegrzyn]

I have a cisco 2821 router configured with NAT to support SIP ALG.

The basic setup looks like this:

int gi0/0

ip address 1.1.1.1 255.255.255.0

ip nat outside

description - inteface facing SIP provider on public internet

intgi0/1

ip address 10.100.0.1 255.255.255.0

ip nat inside

description - interface facing private LAN with OSPF running

default gateway

ip route 0.0.0.0 0.0.0.0 2.2.2.2

static route to provider sip network servers

ip route 3.3.3.3 255.255.255.255 4.4.4.4

To get to private network side (gi0/1)the router uses routes learned through ospf.

router ospf 10

router-id 10.100.0.1

log-adjacency-changes

area 0.0.0.0 authentication message-digest

redistribute static metric-type 1 subnets

network 10.100.0.1 0.0.0.0 area 0.0.0.0

network 10.100.0.0 0.0.255.255 area 0.0.0.0

!

On lan there is different default gateway to get to the internet.

Above router is used to get to the sip provider network only.

I want to be able to distrbute from this router through OSPF only specific 3.3.3.3 route so LAN routes to sip through this router.

In above setup it will work fine, but if the provider has some issues the route will not be removed and the route learned from backup network will have higher metric so not working 3.3.3.3 route will be in the table.

Is there a way to enable some kind of tracking of 3.3.3.3 route and only had it in the routing table when 3.3.3.3 is up?

I know if gi0/0 would be running BGP it would not be an issue but there is no routing protocol on the provider side.

thx

[andrew.prince]

Tracked ip route with an ip sla, with a route map calling an acl to match the route.

Sent from Cisco Technical Support iPad App

[blwegrzyn]

can you show me an example how to accomplish this or provide any good link how this is done?

thx

[Kishore Chennupati]

Hi Bart,

Hope these links helps. Also please note that the commands change with the IOS. So, please check your IOS and you should be able to find the feature

http://docwiki.cisco.com/wiki/IP_SLA_Tracking_with_Configuration_Example

http://www.cciecandidate.com/?p=389

HTH

Regards,

Kishore

Please rate if helps

[Kishore Chennupati · Accepted solution]

Bart,

I have put this in the lab for you. I tested this on a 3640 image.  I have setup a simple network.

    R1<--->  R2    [I configured a loopback on R2 with an ip of 2.2.2.2]

R1#sh run

Building configuration...

Current configuration : 746 bytes

!

version 12.4

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname R1

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

memory-size iomem 5

!

!

ip cef

no ip domain lookup

!

!

ip sla monitor 1

type echo protocol ipIcmpEcho 2.2.2.2

ip sla monitor schedule 1 life forever start-time now

!

!

!

track 1 rtr 1 reachability

!

!

!

!

!

interface FastEthernet0/0

ip address 192.168.1.1 255.255.255.0

duplex auto

speed auto

!

no ip http server

no ip http secure-server

ip route 2.2.2.2 255.255.255.255 192.168.1.2 track 1

line con 0

exec-timeout 0 0

logging synchronous

line aux 0

line vty 0 4

!

!

end

once I shut the loop back on R2 , the static route on R1 disappears.

R1#ping 2.2.2.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:

U.U.U

Success rate is 0 percent (0/5)

R1#sh ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     2.0.0.0/32 is subnetted, 1 subnets

S       2.2.2.2 [1/0] via 192.168.1.2

C    192.168.1.0/24 is directly connected, FastEthernet0/0

R1#

*Mar  1 00:12:46.191: %TRACKING-5-STATE: 1 rtr 1 reachability Up->Down

R1#sh ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

C    192.168.1.0/24 is directly connected, FastEthernet0/0   << static route disapppeared

HTH

Regards

Kishore

Pleaase rate if helps

[blwegrzyn]

thank you guys, tested and worked as expected