Cisco 2620 WIC-1ADSL

[lavinpj1]

Hello,

I have a Cisco 2620 with a WIC-1ADSL card installed. This works all well and good (it can ping and be pinged) with this config:

http://paste.pchowtos.co.uk/?id=1744&key=9924f341fc43d

My ISP has assigned me a /28 of public IPs and requires the router to negotiate an IP with them at the start of each session. They always issue the router the same IP from the start of the /28. On my current setup, using a consumer grade ADSL modem/router, I have a public IP assigned to the Ethernet interface of the device as well as the one negotiated and assigned to the ppp interface. I then use the IP of the Ethernet interface as the gateway for other devices (which have public IPs) on the network.

However, when I try to emulate this setup with the Cisco, by assigning a public IP to the ethernet interface once the ppp has been established, it errors saying that the address overlaps with that of Dialer1.

Can anyone suggest a workaround or better method to allow devices with public IPs to access the outside world?

I have tried setting "ip unnumbered fa0/0" on Dialer1, however this prevents the ip address negotiation that the ISP requires.

Thanks in advance.

 

[burtsbees]

If you want public IP addresses on the WAN and LAN all in the same subnet, you will have to bridge the router and it will then be a layer 2 device only, which is a waste. I would just NAT everything instead of running a dirty DMZ...\

/

 

[lavinpj1]

A dirty DMZ is fine - that's all I want. Could you possibly advise me on how I would be able to bridge like that? I have previously tried bridging by creating a new ieee bridge and assigning fa0/0 (with no IP) to it as well as Dialer1. I then tried bridging fa0/0 (with no IP) and ATM0/0. The IP of ATM0/0 was not pingable in either instance by any device on the fa0/0 side of the router.

Phil

 

[Minue]

Hello
Your desired setup is un-documented so it's going to be difficult to find a work-around.You should speak with your ISP about your problem,and get them to assign you a WAN IP in a different subnet.
As far as the bridging goes,you can try using a BVI interface.The command is "interface bvi 1".

Regards

 

[lavinpj1]

I've thought about using a BVI interface, but I cannot see how I would do such. The IP must be on Dialer1 as that is what negotiates it.

Phil

 

[unclerico]

If you want the "inside" interface and the "outside" interface to share an IP then the only way to make it work is like burt and Minue said and that is to bridge it with a BVI. There is no reason that it can't work.

I hate all Uppercase... I don't want my groups to seem angry at me all the time! =)
- ColdFlame (vbscript forum)

 

[burtsbees]

Actually, I have never tried, but maybe play with "no ip routing"...if I have any time, I can lab something up...but your situation actually provides the best lab and the time to do it...lol

Let us know how it comes out if you succeed soon...

Sorry for being vague, but this is certainly unique...

Burt

 

[lavinpj1]

Hi all,

Thanks very much for the help but I've gotten it working. It just required me to set ip unnumbered fa0/0 on Dialer1, assign the IP manually to fa0/0 and set the ip default-gateway manually also. Only downside is, the ISP expects everyone to use dynamic assignment so if they change the default gateway, things go badly.

Thanks for the help.

Phil

 

[burtsbees]

Tits up is not necessarily a bad thing...right?

If any ISP changes the default gateway, any Cisco router would have to have the ip default-gateway changed as well---the ip add neg does not import that info---it only negotiates an IP address through ppp negotiation via RADIUS, TACACS+ or the like, etc. It is not dhcp...

Burt