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NAT Overload and load sharing

I have a Cisco 2650 with IOS 12.3 (c2600-i-mz.123-16.bin), a fast ethernet, and 2 Int T1 CSU/DSU cards.

Verizon has just enabled the second T-1 line for constant operation--it was previosly just a backup line.

Each T-1 is using frame relay on a serial sub-interface and has ip addresses assigned-- using a /30 subnet. The FA0/0 is defined as ip nat inside and the Serial Sub Interfaces are designated as ip nat outside.

I was using" ip nat inside source list 10 interface s0/0.1 overload" to allow internal users access to the Internet.

I can now use the ip nat pool test netmask 255.255.255.252 address 100.100.100.1 100.100.100.1----ip address s0/0.1 address 100.100.100.5 100.100.100.5 ip address s0/1.1

and

ip nat inside source list 10 pool test overload..

This works but I only get T-1 speed inbound--one or the other serial interfaces-no load sharing. Outbound traffic is equally distributed (I have load-sharing per-packet on each serial sub-interface).

Do I have to get Verizon to bond the T-1 lines or can I use NAT on a stick with some route map magic?

Has anyone setup overload nat to load balance incoming traffic? Not incoming traffic to a server.

It looks as though an internal user will get a global address from the pool, which seems to be the same ip address of the same serial interface and subsequently only goes out a single t-1 circuit.

TIA

Digital Doug

Reply to
Houston SBC
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You only get to control your outbound traffic. Whatever Verizon has to send to you, they get to choose how it's sent.

Not me. Perhaps PPP multilink might help. Makes your 2XT1s look like one interface instead of two.

Yes, for any individual outbound connection. Multiple connections would/might be split between the two addresses so the aggregate b/w might be > 1 x T1.

Reply to
Martin Gallagher

You have a couple ways to do this. However you should coordinate this with your local Verizon loop crews.

  1. You can try to convince them to implement Multilink Frame Relay (you mentioned that you have Frame Relay on the Interface). However if Verizon does not support this, there is nothing you can do.

  1. You can configure a "NAT-on-a-Stick" on your router. Basically it will be doing NAT before it hits Serial Interface, and then process translated packet as a normal routed packet. After you configure NAT-on-a-Stick, you enable IP Load-Sharing (through either CEF or packet processing) to take place on your Serial interfaces.

  2. You should also talk to Verizon, how do they do load-balancing on your links. You may need to do something more complicated, like BGP.

Good luck,

Mike

------ Headset Adapters for Cisco IP Phones

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Reply to
headsetadapter.com

And here is a link for NAT-on-a Stick configuration:

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Good luck,

Mike

------ Headset Adapters for Cisco IP Phones

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Reply to
headsetadapter.com

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