Internet traffic control

Answered Question

Hi friends,

I have 3 internet links 2x25M and 1x50 M .I have 3 different LAN subnets(Public).How can I assure that traffic to and from first subnet use first link second subent use second link and thrid subnet use thrid link .whats the config requured for this

Regards

V

I have this problem too.
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Correct Answer by gatlin007 about 6 years 7 months ago

To use those links as efficiently as possible I recommend using BGP and receiving the full routing table from your upstream.  Cisco OER is a great feature that works will with balancing traffic between disparate circuit sizes.

http://www.cisco.com/en/US/docs/ios/oer/configuration/guide/12_4t/oer_12_4t_book.html


Christopher Gatlin
http://travelingtech.net

Correct Answer by Calin Chiorean about 6 years 7 months ago

You can use PBR to influence the traffic outgoing (you cannot influence the inbound traffic with this method)


-make an ACL matching source subnet-1 to destination ANY

-match the ACL in a route-map

-in the route-map "set ip next-hop POP1-IP"

-apply the route-map under the LAN interface with "ip policy route-map NAME-OF-ROUTE-MAP"

More about PBR:

http://www.cisco.com/en/US/products/ps6599/products_white_paper09186a00800a4409.shtml

Configuration:

https://www.cisco.com/en/US/docs/ios/12_0/qos/configuration/guide/qcpolicy.html

Then with BGP, you can influence inbound and outbound traffic.

The procedure is something like:

-match interesting traffic in ACL1 (for subnet-1) ACL2(for subnet-2)

-match ACL in route-maps (one for inbound and one for outbound / peering)

-in each route-map modify the some BGP attributes (depending if inbound or outbound one as-path, MED, local-preference....) so the one subnet is more prefered on the primary POP than on the rest

-apply route-maps in and out to the 3 peerings corresponding to the three POPs.

More on BGP attributes:

http://www.cisco.com/en/US/docs/internetworking/technology/handbook/bgp.html

I didn't asked, but you have theree point to point links there on the WAN link, right? One for each POP.

Let me know if this helps.

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Calin Chiorean Wed, 06/09/2010 - 01:38

I understand your problem, but we need some more details in order to be able to help, because the solution depends on the following:

- how you connect to the ISP (e.g. one router with three interfaces or multiple routers)

- the 3 lines are offered by one ISP or multiple ones

- how do you receive your routes from ISP; default route or dynamic protocol with BGP (if BGP, you receive default route or full routing table)

- local subnets are public IP addresses or private ones (192.168.x.x, 172.16.xx, 10.x.x.x).

Now, some solution would be:

- if you have 3 private subnets in the LAN and 3 public IP addresses from ISP, you can NAT one to one (one private subnet to one public IP corresponding to one internet line)

- if you have BGP there you can influence with BGP attributes what path to take each subnet (in case of public IP addresses in LAN subnets)

- another option would be PBR

Please give us the details and we will help!

Calin

Hi Calin,

Thanks for your prompt reply

All 3 links are terminating on same CE.Other end is single ISP but terminating on 3 different PoP routers.

LAN subnets are Public IP.

no requirement of full routing table.

Ready to run BGP if required(let me know if other options available without running BGP)

let me know if aything missing

Correct Answer
Calin Chiorean Wed, 06/09/2010 - 02:23

You can use PBR to influence the traffic outgoing (you cannot influence the inbound traffic with this method)


-make an ACL matching source subnet-1 to destination ANY

-match the ACL in a route-map

-in the route-map "set ip next-hop POP1-IP"

-apply the route-map under the LAN interface with "ip policy route-map NAME-OF-ROUTE-MAP"

More about PBR:

http://www.cisco.com/en/US/products/ps6599/products_white_paper09186a00800a4409.shtml

Configuration:

https://www.cisco.com/en/US/docs/ios/12_0/qos/configuration/guide/qcpolicy.html

Then with BGP, you can influence inbound and outbound traffic.

The procedure is something like:

-match interesting traffic in ACL1 (for subnet-1) ACL2(for subnet-2)

-match ACL in route-maps (one for inbound and one for outbound / peering)

-in each route-map modify the some BGP attributes (depending if inbound or outbound one as-path, MED, local-preference....) so the one subnet is more prefered on the primary POP than on the rest

-apply route-maps in and out to the 3 peerings corresponding to the three POPs.

More on BGP attributes:

http://www.cisco.com/en/US/docs/internetworking/technology/handbook/bgp.html

I didn't asked, but you have theree point to point links there on the WAN link, right? One for each POP.

Let me know if this helps.

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