Question about PPPoE and DNS

Unanswered Question
May 14th, 2007

I've got a Cisco1841-AdvansedSecurity (don't ask me what for) and PPPoE connection through Ethernet-DSL modem.

Before 1841 I've used IPcop-Linux Firewall. When PPPoE connection starts, Linux automatically recieved couple of DNS server from ISP, so I don't have to add it manually.

Is there a way to keep same thing in 1841, without "ip name-server bla.bla.bla.bla"?

Right now my config looks that way:

vpdn enable

!

vpdn-group 1

!

!

interface FastEthernet0/1

description WAN connection

no ip address

duplex auto

speed auto

pppoe enable group global

pppoe-client dial-pool-number 1

!

interface Dialer1

mtu 1492

ip address negotiated

ip virtual-reassembly

encapsulation ppp

ip tcp adjust-mss 1452

dialer pool 1

dialer-group 1

keepalive 120 20

no cdp enable

ppp authentication chap callin

ppp chap hostname LOGIN

ppp chap password PASSWORD

!

ip route 0.0.0.0 0.0.0.0 Dialer1

I have this problem too.
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mohammedmahmoud Mon, 05/14/2007 - 14:11

Hi,

AFAIK, this can't be done on a cisco router, "ip address negotiated" negotiate the IP address only.

Plus the "ip name-server" command doesn't need any frequent changes, its a one time configuration command, it shouldn't be a problem.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

vpmorozov Tue, 05/15/2007 - 09:58

Hello, Krisztian!

I've added "ppp ipcp dns request accept" and "ppp ipcp predictive", now router resolves address without "ip name-server", so - this method WORKS! :-)

But I found 2 new questions:

1. DDNS tries to update HTTP address BEFORE router gets DNS through PPP IPCP. And I've not found any way to suspense DDNS update for a couple of seconds. Using workaround - added "ip host members.dyndns.org I.P.ADD.RESS"

2. How can I use DNS, obtained throug PPP IPCP, in DNS spoofing (DNS proxy) for my LAN clients, which uses router IP as DNS.

Thanks a lot, your first advice was very useful! :-)

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