Redondant WAN routing and priority route for a specific TCP port

[Mario Lessard]

Hi,

    I would like to balance traffic on 2 route. For exemple, I have 2 router on site and to other site I have two other router. I create route between router 1 router to other router and an other route with 2 other router. So, in fact, I have two different route to communique with both site (a redondant WAN with 4 routers).

    Ok, normaly, EIGRP will determine witch line will be the best to communicate. But, I would like to split my communication on both line. So, what I want to do is I would like to specify a TCP port on the line in theoric slower then the principal to use this line. So, when this slower line will be down, the 100% traffic will pass on principal line. In normal use, the TCP port number 1000 will use route B and all ohter traffic will use route A. With this way, it will be possible for me to balance a little bit my lines.

Thank you

[Giuseppe Larosa]

Hello Mario,

what you would like to achieve is possible with PBR Policy Based Routing

access-list 111 permit tcp any any eq 1000

route-map PBR pemit 10

match ip address 111

set ip next-hop b.b.b.b

where b.b.b.b is the IP next-hop on link B, all other traffic uses Link A

int type x/y/z

description LAN interface receiving traffic to be redirected

ip policy route-map PBR

A similar PBR rule should be applied on the other side using an ACL matching on source port 1000

access-list 112 permit tcp any eq 1000 any

Hope to help

Giuseppe

[Mario Lessard]

Thank you for your answer,

A question, I think with this solution is when Link B goes down TCP port number 1000 stop to communicate?

Let me know

Thank you

[Alessio Andreoli]

Hi mario,
Giuseppe was suggesting to apply the PBR policy on the second link by means of acl 112 exactly to keep the tcp port 1000 in forwarding. You can, however, assign priorities to one link rather than the other if you want to load-share the aggregate outbound traffic for example.

Sent from Cisco Technical Support iPad App

Alessio

[Giuseppe Larosa]

Hello Mario,

good note

PBR will be used if the IP next-hop on Link B is reachable,

you can add the

set ip next-hop verify-availability

in route-map PBR configuration to improve this detection (support of the command is platform and IOS dependent)

If the Link B fails the traffic is routed by EIGRP on Link A, that is the traffic is destination based routed using your IGP.

Link A has to be the preferred link for EIGRP (better metric), using PBR you can move some selected traffic to/from Link B, when link B is available.

Hope to help

Giuseppe

[Joseph W. Doherty]

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Posting

Another approach would be use EIGRP to proportionally balance your links and then use QoS to treat TCP port 1000 traffic "differently".

If the links are close to being the same in bandwidth, you might just equally load balance them.

If the links are different in bandwidth, you could also consider using the PIRO feature of PfR to dynamically balance them, while still using QoS for treatment.  This last approach might be the best as it dynamically uses both links bandwidth optimally.