DHCP Question

[jonny2495]

Hi Guys,

I will be starting a CCNA course next month and have bought myself a 2514 to use on my broadband. I am going to use it to replace the linux router I have been running.

I have come across a problem that I hope someone on here can help me with.

I am setting the router up in stages and have been configuring ethernet 0 to obtain its IP address etc from my ISP via DHCP. If I connect it to my existing router it gets an IP address and will ping various web servers etc.

However, if I connect it directly to my DSL modem it obtains the correct IP address but fails to resolve addresses and it cant ping the DNS server, dhcp server etc that I know are there because its got an IP address from them.

Heres what I have in my config:

!
version 12.2
service timestamps debug uptime
service timestamps log uptime
service password-encryption
!
hostname Router
!
enable secret
enable password
!
ip subnet-zero
!
!
!
!
interface Ethernet0
description WAN
ip address dhcp
!
interface Ethernet1
no ip address
shutdown
!
interface Serial0
no ip address
shutdown
!
interface Serial1
no ip address
shutdown
!
ip classless
no ip http server
ip pim bidir-enable
!
!
line con 0
line aux 0
line vty 0 4
exec-timeout 30 0
password
login
!
end

I will be adding NAT and firewalling when I get this sorted.

Any help will be appreciated.

Thanks

Jon

 

[JOAMON]

I beleive you need to configure the router for PPPOE when directly connecting it to the modem. You setup a dialer interface and then use IP address negotiated. For your lan DHCP you then use import all so the clients get the DNS information from the router.

 

[jonny2495]

Hi Joamon

Thanks for the response. My modem handles all the encapsulation etc and that side is working OK. The communication side is working OK as I am getting an IP address from my ISP.

Having had a futher play around I have realised that when I plug it into my other router it gets an IP address and sets the default route to the other router. When I attach it to the modem it gets an IP address but assignes the default route to the same ip address rather than the ip address of the ISP's gateway.

I am pretty sure this is causing the problem but have no idea about how to fix it.

Jon

Jon - CCNA to be
UK

 

[JOAMON]

Did you try connecting the 2514 to the modem in power down state and bring it up live when connected to the DSL modem?

 

[t0mm0]

I believe you're in a similar situation to this Guy;

http://www.tek-tips.com/viewthread.cfm?qid=1257006

Whereby you'll have to create a NAT on your LAN interface and cross ref it to your access list, which I imagine will include your DNS server..

 

[jonny2495]

Hi T0mm0

I had read that post and tried to see if it would affect my set up but it didnt help.

The NAT and LAN side of things Iam OK with. I have already tried that and it orks great. Because of the problems I am having with on the WAN interface I have removed all other config to try and eliminate as many possible casues as possible.

I will have to spend some time over the weekend going back to basics.

Cheers

Jon

Jon - CCNA to be
UK

 

[plshlpme]

the 2514 can do pppoe... youde be better off to put the modem back to bridged mode and then create a dialer on the router to obtain your ip..

also for dns i usually don't give the router dns knowledge.. i just take the know dns servers from my isp and put them into the dhcp for the clients..

i can post the config from my 2514 if youde like with the dialer etc... but ide have to go power it on first.
i recently upgraded to a 1760 which handles the traffic much better.

 

[jonny2495]

I never thought of putting my moem in bridged mode, thanks!

If you could post your config that would be great.

Cheers

jon

Jon - CCNA to be
UK

 

[plshlpme]

Hey, i haven't had a chance to get my config but i quickley googled and found another guys config..

http://www.kvedulv.de/cisco-howto.html

very similar setup. i scraped some of his ip6 stuff out.
take a look at this and if you have any q's just let me know.


version 12.3
no parser cache
no service pad
service timestamps debug uptime
service timestamps log uptime
service password-encryption
!
ip subnet-zero
no ip source-route
ip cef
!
vpdn enable
!
vpdn-group 1
request-dialin
protocol pppoe
!
interface Ethernet1
description WAN ADSL Interface
no ip address
no ip proxy-arp
no ip mroute-cache
pppoe enable
pppoe-client dial-pool-number 1
no cdp enable
!
interface Ethernet1
description LAN Interface
ip address x.x.x.x y.y.y.y (LAN INTERNAL IP)
no ip proxy-arp
ip nat inside
no ip mroute-cache
no cdp enable
!
interface Serial0
no ip address
no ip mroute-cache
shutdown
no cdp enable
!
interface Serial1
no ip address
no ip mroute-cache
shutdown
no cdp enable
!
interface Dialer1
description ADSL DIALER
ip address negotiated
no ip proxy-arp
ip mtu 1492
ip nat outside
encapsulation ppp
ip tcp adjust-mss 1452
dialer pool 1
dialer-group 1
no cdp enable
ppp authentication chap callin
ppp pap sent-username xxx password 7 xxx
!

ip nat inside source list 10 interface Dialer1 overload


<<<the rest are just examples of some port mapping (PAT) for applications>>>

ip nat inside source static tcp 192.168.200.17 1214 interface Dialer1 1214
ip nat inside source static tcp 192.168.200.11 22 interface Dialer1 22
ip nat inside source static tcp 192.168.200.17 6881 interface Dialer1 6881
ip nat inside source static tcp 192.168.200.17 6882 interface Dialer1 6882
ip nat inside source static tcp 192.168.200.17 6883 interface Dialer1 6883
ip nat inside source static tcp 192.168.200.17 6884 interface Dialer1 6884
ip nat inside source static tcp 192.168.200.17 6885 interface Dialer1 6885
ip nat inside source static tcp 192.168.200.17 6886 interface Dialer1 6886
ip nat inside source static tcp 192.168.200.17 6887 interface Dialer1 6887
ip nat inside source static tcp 192.168.200.17 6888 interface Dialer1 6888
ip nat inside source static tcp 192.168.200.17 6889 interface Dialer1 6889
ip nat inside source static tcp 192.168.200.17 4661 interface Dialer1 4661
ip nat inside source static tcp 192.168.200.17 4662 interface Dialer1 4662
ip nat inside source static udp 192.168.200.17 4665 interface Dialer1 4665
ip nat inside source static udp 192.168.200.17 4672 interface Dialer1 4672
ip nat inside source static tcp 192.168.200.42 6346 interface Dialer1 6346
ip nat inside source static tcp 192.168.200.42 666 interface Dialer1 666
ip nat inside source static tcp 192.168.200.11 80 interface Dialer1 80
ip nat inside source static tcp 192.168.200.23 23 interface Dialer1 23
ip nat inside source static tcp 192.168.200.254 2001 interface Dialer1 2001
ip nat inside source static tcp 192.168.200.254 6001 interface Dialer1 6001
ip nat inside source static tcp 192.168.200.11 1881 interface Dialer1 1881
ip nat inside source static tcp 192.168.200.11 1882 interface Dialer1 1882
ip nat inside source static tcp 192.168.200.11 1883 interface Dialer1 1883
ip nat inside source static tcp 192.168.200.11 1884 interface Dialer1 1884
ip nat inside source static tcp 192.168.200.11 1885 interface Dialer1 1885
ip nat inside source static tcp 192.168.200.11 1886 interface Dialer1 1886
ip nat inside source static tcp 192.168.200.11 1887 interface Dialer1 1887
ip nat inside source static tcp 192.168.200.11 1888 interface Dialer1 1888
ip nat inside source static tcp 192.168.200.11 1889 interface Dialer1 1889
ip nat inside source static tcp 192.168.200.1 1024 interface Dialer1 1024
ip nat inside source static udp 192.168.200.1 1024 interface Dialer1 1024
no ip http server
ip classless
!
ip route 0.0.0.0 0.0.0.0 Dialer1
!
!
no logging trap
access-list 10 permit x.x.x.x y.y.y.y (lan subnet)
no cdp run

 

[jonny2495]

Hi Guys,

I had a play around with this now and am still having problems.

I am using IOS 12.2 and dont seem to be able to use vpdn.

Also my broadband provider uses PPPOA so another thing I am going to have to read up on.

Jon

Jon - CCNA to be
UK

 

[plshlpme]

i was suing c2500-is-l.122-15.T14.bin

 

[jonny2495]

I only have a couple of 12.2 images and I dont think any of them have vpdn.

Is there somewheer I can get 2500 images?

Cheers

Jon - CCNA to be
UK