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MultiHomed Internet Access

Hi All,

I have Microsoft Exchange 2000 Server (based on MS Windows 2000 Server and running behind MS ISA 2000 Server) connected to two routers.

One of them is a Cisco 1751-V model with Serial WIC used for Internet Access and VoIP. This internet access service is PPP WAN connection based, and has fixed external IP's.

Because we had QoS problems using VoIP over Internet, we decided to put another cheap Zyxel router-switch connected to ADSL Internet Service with dynamic IP's.

I have put both routers in the same subnet. The 1751-V has "x.y.z.209" and the ADSL has "x.y.z.219" IP LAN address.

So well, at first I had problems because the MS ISA Server (Web Proxy and Firewall) only recognise one default gateway. I choose to put as default gateway the "x.y.x.219" and everything goes well (web browsing, e-mail outgoing, vpn service, the web site) - except for ingoing mail.

The mail's simply don't enter when I use the x.y.z.219 default gateway on the server. When I put x.y.z.209 as default gateway everithing goes great, but there is a degradation of VoIP services as it runs from 209 IP.

I would like to discuss if someone knows how to redirect the ingoing mail from the Cisco 1751-V router to the server's external IP (x.y.z.212), without the need of default gateway for that PC.

An important information is that there is response to the command "ping x.y.z.212" (my server) from the Internet.

Any comment will be welcome.

Best Regards,

Igor Sotelo.

New Member

Re: MultiHomed Internet Access


The ingoing e-mail traffic will not pass through the Non-Cisco gateway since it has a dynamically assigned address, and the SRV DNS record will point towards the 1751 address. As for the VoIP degradation, you can use the "ip rtp priority" to increase the priority for the voice traffic on the Cisco router.

Hope I helped

New Member

Re: MultiHomed Internet Access


Thank you for the QoS advice, but on Internet the QoS is difficult. I could solve the multihomed problem, by puting this commands on the Cisco router:


access-list 101 permit tcp any any eq www

access-list 101 permit tcp any any eq 443

access-list 101 permit tcp any any eq smtp

access-list 101 permit tcp any any eq ftp

access-list 101 permit tcp any any eq pop3


route-map ADSL

..match ip address 101

..set ip next-hop


interface FastEthernet0

..ip policy route-map ADSL

On the server we returned the original x.y.z.209 default gateway.

I saw a similar configuration in another post, and it works fine.

About the ADSL router, it has an Internal IP address that is fixed, but is translated always differently by our ISP.

Best Regards,

Igor Sotelo.

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