HSRP & EIGRP

msaulnier · ‎08-30-2007

I have 3 routers A, B and C

All 3 routers are connected by vlan 2

This is there address on vlan 2:

A 172.17.4.31

B 172.17.4.33

C 172.17.4.63

B and C have vlan6 and are configured with HSRP

B 10.30.30.33

C 10.30.30.63

HSRP 10.30.30.70 (C is active)

Router A is learning network 10.30.30.0 with EIGRP

Routing entry for 10.30.0.0/19

Known via "eigrp 100", distance 90, metric 28416, type internal

Redistributing via eigrp 100

Last update from 172.17.4.63 on FastEthernet0/1, 00:36:09 ago

Routing Descriptor Blocks:

* 172.17.4.33, from 172.17.4.33, 00:36:09 ago, via FastEthernet0/1

Route metric is 28416, traffic share count is 1

Total delay is 110 microseconds, minimum bandwidth is 100000 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 1

172.17.4.63, from 172.17.4.63, 00:36:09 ago, via FastEthernet0/1

Route metric is 28416, traffic share count is 1

Total delay is 110 microseconds, minimum bandwidth is 100000 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 1

I want router A to choose the active router (172.17.4.63) not the standby. What should I do?

Jon Marshall · ‎08-30-2007

Hi

Can you do a

"sh ip route | begin 10.30.0.0 255.255.224.0"

I ask because i believe that both paths will be being used as they are equal cost so EIGRP will install both into the routing table.

The other thing i would say is that routers do not use HSRP, this is for end devices only. Routers uses the physical interface addresses.

If you really want to ensure that all traffic goes via the active HSRP router you could use metrics or PBR but these would not dynamically change if the active interface goes down. Is there a reason you want to do this ?

Edit - should also have said the asterix in the output next to the 172.17.4.33 entry is not signifying the chosen route rather the asterix moves between the 2 routing entries as each route is used to forward packets.

Jon

msaulnier · ‎08-30-2007

The reason I want to do this... I didn't want to have asymmetrical routing. But I think I don't really need to.

sh ip route | begin 10.30.0.0

D 10.30.0.0/19 [90/28416] via 172.17.4.33, 02:49:24, FastEthernet0/1

[90/28416] via 172.17.4.63, 02:49:24, FastEthernet0/1

Mohamed Sobair · ‎08-30-2007

Hi,

By default Eigrp will load balance across equal cost paths, but as you posted, its not load balancing a cross both paths.

To view all paths available for the Network 10.30.0.0/19, issue (sh ip eigrp topolgy) command. and since you have one active route in the routing table, it does mean its a successor. A feasable successor is a vailable second path can be used with the (variance command).

In your case, you want the router to take the other path for Network 10.30.0.0/19, you can acheive this by higher the delay of Router' B Interface as follows:

Interface x

delay 120

* Be carefull not increasing the delay of the interface two much till the route wont be seen as Feasible Successor.

Another way, is to configure (Offest-List) and & increase the Delay of Specific Network as follows:

Router-B

router eigrp 100

offest-list 10 out 20 interface x

access-list 10 permit 10.30.0.0 0.0.31.255

This will increas the delay of subnet 10.30.0.0/19 by 20 when the router sends an Eigrp update, so when it reaches router A, Router A will decide to go through router-C to reach Network 10.30.0.0/19

HTH

Regards,

Mohamed Sobair

Jon Marshall · ‎08-30-2007

Hi Mohamed

It is load balancing across both links. If you look at the output of the "sh ip route | begin 10.30.0.0" you can see that EIGRP has installed 2 routes for the destination subnet into the routing table. So there are two active routes in the routing table.

And from the output of the original post you can see that both routes have an equal cost so the concept of a feasible successor does not come into play.

So yes, as i said you can influence this with metrics but why would you want to. If you do per-destination load-balacing then asymetric routing is not an issue anyway.

Jon

Mohamed Sobair · ‎08-31-2007

Hi Jon,

Apologize,

I didn't see the next active route, yes its load sharing accross both paths.

But As I understand, his objective is to make sure the returned traffic is coming through the Active Router,so the this has nothing to do with HSRP but Metric influencing, AM I Right?

Or correct me if I mistaken or mis understood some thing.

Regards,

Mohamed Sobair

Jon Marshall · ‎08-31-2007

Hi Mohamed

No need to apologize at all. Just wanted to point out that it was using both paths.

You are right but i think the original poster assumed that it was using only the standby router and it was in fact using both. And i was trying to emphasize that EIGRP as a routing protocol does not use HSRP.

The metric solution you gave would work fine but i just wondered why do that ?

Jon

Mohamed Sobair · ‎08-31-2007

Hi Jon,

Yes you are right, since HSRP is independent Of EIGRP traffic in his case.

May be he just have specific approach or some thing in mind, but I agree with u your point is definetly valid.

Regards,

Mohamed Sobair