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Webcast-Catalyst9k
New Member

Setting 2 default routes in a router

I have 2 V.35 E1 lines connected to same ISP access router. So, how should I implement the load sharing between the 2 E1 lines?

interface serial 1/1

Description E1 line to ISP

ip addrress 203.101.1.1 255.255.255.252

!

interface serial 1/2

Description E1 line to ISP

ip addrress 203.101.1.5 255.255.255.252

!

ip route 0.0.0.0 0.0.0.0 203.101.1.2

ip route 0.0.0.0 0.0.0.0 203.101.1.6

!

Can I load balance the 2 E1 lines using the method shown above?

Or

I should do like this:

interface serial 1/1

Description E1 line to ISP

ip addrress 203.101.1.1 255.255.255.252

ip load-sharing per-packet

!

interface serial 1/2

Description E1 line to ISP

ip addrress 203.101.1.5 255.255.255.252

ip load-sharing per-packet

!

ip route 0.0.0.0 0.0.0.0 203.101.1.2

ip route 0.0.0.0 0.0.0.0 203.101.1.6 120

!

4 REPLIES
New Member

Re: Setting 2 default routes in a router

Both will work. The second config will load balance better I think, because it will distribute the load. The first config is a per session type load balancing, which can load one leg over the other.

Bronze

Re: Setting 2 default routes in a router

I'd use the first config with two default static routes.

ip route 0.0.0.0 0.0.0.0 203.101.1.2

ip route 0.0.0.0 0.0.0.0 203.101.1.6

Note CEF will do per-destination load balancing by default. To use per-packet load balancing use the ip load-sharing per-packet command as you did on the second config.

more info of CEF load balancing:

http://www.cisco.com/en/US/tech/tk827/tk831/technologies_tech_note09186a0080094806.shtml

Be sure to read the caveats of using per-packet load sharing...

HTH

New Member

Re: Setting 2 default routes in a router

Well,

both work , but only for outbound traffic from your router towards ISP.

For inbound traffic ISP has to configure the similar way in their router.

However in the first case, the default load sharing (per destination) is recommended only if you are running any real time applications (voice/video)over these links, which does not support per-packet load sharing.

Else I would suggest to go with second config per-packet load sharing, which gives perfect load-balancing of the traffic.

New Member

Re: Setting 2 default routes in a router

hi,

if you use the second methode, then the router will only forward packets to 203.101.1.2 because the route to 203.101.1.6 has a admin. distance of 120.

a normal static will have 1 - so the first route will be used (x.x.x.2)

if the int goes down (to x.x.x.2) the second route (x.x.x.6) will be used.

if this is what you want - then its ok.

if you want to make real load-balancing the you don´t need to have the admin distance of 120 - so all two defaultroutes will be used.

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