I want achieve a load balancing of ISP like the one below.Diagram

Only 2 subnet should go through ISP 2, and rest of the traffic should go to ISP 1.

Let me know all the things that I need to do on a 3750x core and firewall. Waiting for your response......

  • Just use a route map which matches your subnet using an ACL and set next-hop address (try this doc: cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/54sg/…). There're so many resources on that. What did you try to do?
    – Alex
    Sep 5, 2014 at 6:56
  • HI , Thanks for your reply, what i am trying to do is, that one of my subnet should go through isp 2 and rest all the subnet traffic will go thro isp 1 -- - - suppose there are 3 subnet (ABC), I want subnet A&B should go through ISP1 and Subnet C will go thro ISP2.
    – Spei043
    Sep 5, 2014 at 7:05
  • Then it's exactly described in the document I mentioned above. Create a route-map, match traffic (you create an ACL for that), set next-hop, apply r-m to an interface.
    – Alex
    Sep 5, 2014 at 7:45
  • 1
    Thanks, but does it will support on IPBASE 3750x AND ALSO there are too much on the link, can u give me one sample config of 3 subnet in which 1 subnet for isp 2 and 2 subnets for ISP 1., it will be great help for me
    – Spei043
    Sep 5, 2014 at 8:01
  • 1
    Do you have either a provider independent block of IPs or portable address space? Sep 5, 2014 at 8:24

2 Answers 2


If you only want outbound traffic to be load-balanced like that (beware inbound traffic from the Internet won't be affected and will be routed according to Internet routing tables) then let's suppose your ASA1 IP address is and ASA2 address is

Two subnets that should go through ISP 2 are:

Everything else goes through ISP1

Then you create two ACLs:

access-list 101 permit
access-list 101 permit

Create a route-map (last permit line is to match all remaining traffic and route by default):

route-map pbr1 permit 10
  match ip address 101
  set ip next-hop
route-map pbr1 permit 20
  set ip next-hop

Apply to inbound interface facing the local subnets:

interface GigabitEthernet 0/1
  ip policy route-map pbr1

Hope that helps a little bit. Some more helpful resources for you:

Also you can see if PBR is supported on your 3750x on Cisco's Feature navigator.

  • HI Alesx Thanks for the information.....will try to implement and update u.
    – Spei043
    Sep 5, 2014 at 9:22
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    Guys, i guess, there is one more imoprtant command: sdm prefer routing. This will tune TCAM buffers for routing purpouses
    – pyatka
    Sep 5, 2014 at 10:17
  • Hey I didn't even know about this one!
    – Alex
    Sep 5, 2014 at 10:58
  • currently its default and IP Base image is running so do we need to run this command
    – Spei043
    Sep 5, 2014 at 11:36
  • I think this is a decent one on sdm prefer command: cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/…
    – Alex
    Sep 5, 2014 at 11:54

I´m agree with the explanation of Alex, but if you do that, the you must set a modification because if for some reason, one of the two links fails, the pbr mus continue matching traffic, and may occurs that, the traffic flow searching the next-hop of the link down, in other words, a blackhole inside your network.

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