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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......

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  • 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 '14 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 '14 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 '14 at 7:45
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    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 '14 at 8:01
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    Do you have either a provider independent block of IPs or portable address space? – Mike Pennington Sep 5 '14 at 8:24
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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 192.168.0.1/30 and ASA2 address is 192.168.0.5/30.

Two subnets that should go through ISP 2 are:

192.168.1.0/24
192.168.2.0/24

Everything else goes through ISP1

Then you create two ACLs:

access-list 101 permit 192.168.1.0 0.0.0.255
access-list 101 permit 192.168.2.0 0.0.0.255

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 192.168.0.5
route-map pbr1 permit 20
  set ip next-hop 192.168.0.1

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.

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  • HI Alesx Thanks for the information.....will try to implement and update u. – Spei043 Sep 5 '14 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 '14 at 10:17
  • Hey I didn't even know about this one! – Alex Sep 5 '14 at 10:58
  • currently its default and IP Base image is running so do we need to run this command – Spei043 Sep 5 '14 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 '14 at 11:54
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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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