Manipulate incoming and outgoing traffic

[farhannadeem507]

Hello guys 

Hop all are doing will. 

Suppose two ISP links(ISP1 & ISP2) are terminated on a router and by default incoming and out going traffic are using ISP1 link but we need to manipulate this traffic our requirement is that when traffic come in our LAN then it should be used ISP 1 and when traffic will go from our the LAN to WAN then it should be use ISP2 link so can someone please let me know how can we do this type manipulation ? 

[Enes Simnica]

hello @farhannadeem507 . to make incoming traffic use ISP1 and outgoing traffic use ISP2, you can use Policy-Based Routing (PBR). Because by default, ur router uses ISP1 for both directions, but PBR lets u override this for specific traffic.

First, create an access-list to match your LAN traffic (some like access-list 100 permit ip LAN_SUBNET). Then, define a route-map to force outgoing traffic through ISP2: and try this config:

route-map PBR permit 10  
 match ip address 100  
 set ip next-hop ISP2_GATEWAY  
and G apply this routemap to ur lan interface also:
int g0/1
ip policy route-map ...

 and thiss will ensure the icoming traffic stays on ips1 while the outgoing one uses isp2... 

https://www.cisco.com/c/en/us/td/docs/routers/asr920/configuration/guide/iproute/iri-xe-3s-asr920-book/iri-xe-3s-asr920-book_chapter_01.pdf and I can lab this on EVEng, just let me know...... hope it helps

-Enes

[MHM Cisco World]

Are you use bgp?

Are you sure there is no FW config that drop asymmetric traffic?

Why you not think about load sharing ?

MHM

[MHM Cisco World]

Sorry 

Let other VIP help you

I busy now and maybe I can not reply to you fastly 

Thanks 

MHM

[Enes Simnica]

also @farhannadeem507 i found this link, and its about Influencing Forwarding Behavior with Policy Based Routing...check it out...:

https://blogs.cisco.com/learning/influencing-forwarding-behavior-with-policy-based-routing

[paul driver]

Hello
why would you want intentionally to create asymmetrical routing - what is that beneficial for?

I would say if you wish to utilise both isp paths then you could load balance your lan traffic and there are various ways to accomplish it depending on thre kind of topology your are running

However you don’t mention how you are connecting to these ISPs  what routing process your using - are you receiving full/partial route tables do you have any network translation or any other services that may be impacted with this requirement?

Could you elaborate please ?

[farhannadeem507]

Thank you to all for your best support. 

[Joseph W. Doherty]

. . . please let me know how can we do this type manipulation ? 

Do I understand correctly, you want all traffic to the Internet to only use ISP2 and all traffic into your network to only use ISP1?

If so, traffic to the Internet might be as simple as using a default route, only using ISP2, and for your Internet public IP(s) only be advertised by ISP1, which would also be the only path used for traffic from the Internet.

One issue, unless you have your own public IP(s), if you have two public IPs, IPs provided by ISP1 and ISP2, how the Internet links connect to a single router can be problematic, as the traffic flowing to the Internet, out via ISP2 needs to have the public IP(s) of ISP1.

As noted in other replies some form of load balancing would possibly take better advantage of your dual ISPs, and you haven't defined what to do if either ISP1 or ISP2 path fails.  That too can get complicated if using ISP public IPs.