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Community Member

Question about PPPoE and DNS

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

5 REPLIES

Re: Question about PPPoE and DNS

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.

Silver

Re: Question about PPPoE and DNS

Hi,

Try the "ppp ipcp dns request" command under the dialer interface so it will force the 1841 to request dns server IP during the ppp establishment.

Pls rate if helps.

Thanks,

Krisztian

Community Member

Re: Question about PPPoE and DNS

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! :-)

Silver

Re: Question about PPPoE and DNS

Hi,

Happy to help :)

Take look at this link:

http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00801a7605.html

Pls rate if helps,

Krisztian

Community Member

Re: Question about PPPoE and DNS

I've figured out that I don't have to use DNS spoofing, DNS server is enough :-)

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