Cisco 877 Unnumbered

[bdlamprecht]

I am trying to setup an 877 router in unnumbered mode and cannot seem to find what I am doing wrong. From the router console I can ping the outside world fine, but on the LAN side, nothing gets through, not even to the IP address of the dialer0 interface.

Here is my config if anyone can help:

!
version 12.4
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname ****
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
resource policy
!
ip subnet-zero
ip cef
!
!
!
!
!
username ******* privilege 15 secret 5 ****
!
!
!
!
!
interface ATM0
no ip address
shutdown
no atm ilmi-keepalive
pvc 0/32
encapsulation aal5mux ppp dialer
dialer pool-member 1
!
dsl operating-mode auto
!
interface FastEthernet0
!
interface FastEthernet1
!
interface FastEthernet2
!
interface FastEthernet3
!
interface Vlan1
no ip address
!
interface Dialer0
ip address negotiated
ip virtual-reassembly
encapsulation ppp
dialer pool 1
dialer-group 1
ppp pap sent-username ****@**** password 0 ******
!
ip classless
ip route 0.0.0.0 0.0.0.0 Dialer0
!
no ip http server
no ip http secure-server
!
dialer-list 1 protocol ip permit
!
control-plane
!
!
line con 0
logging synchronous
login local
no modem enable
line aux 0
login local
line vty 0 4
login local
!
scheduler max-task-time 5000

 

[bdlamprecht]

Note: The interface atm0 is shutdown in the above config, but when that is enabled, the problem still exists.

 

[DanInRaleigh]

dont you have to have an access-list associated with dialer pool/dialer group # that allows specific subnet?


i'm running 2600. lil differnt in the setup..but maybe not..


my access list 1 is associated with the dialer... i think. ...been a while since i set up..

access-list 1 permit 192.x.x.0 0.0.0.255

http://daniel-white.com

 

[DanInRaleigh]

........not sure because your going the unumbered route..
....or because this is 877..
......and seeing you are authenticating to ISP..
...would you not use nat?
..thanx daniel

http://daniel-white.com

 

[bdlamprecht]

The "dialer-list 1 protocol ip permit" should allow all ip traffic to go across the dialer and atm interfaces. I know if you want to use NAT you have to implcitly allow want you want in an ACL, but I don't think that is the case here. I don't want to use NAT or DHCP. I believe I need to find a way to bridge between the dialer0 and LAN interfaces but I am not sure if that is the right direction. Thanks for you help thus far and any more pointers would be appreciated.

 

[Jimtron26]

Hi zebsc,

Shouldn`t you give the VLAN 1 interface an IP address on your local network?

Why are you trying to bridge between the two interfaces? The IP Unnumbered feature allows an interface to assume the IP address of another however, internal hosts will not be able to ping your public IP address as they have no gateway to reach it.... or am I missing something here??!

(I have configured the newer 8** series routers and the traditional fa0/0 has been replaced by the VLAN interface - the fa0/0 ports on these routers are merely switch ports)

Hope this helps!

Jim

 

[bdlamprecht]

I know I could assign the VLAN1 interface an IP address, but by doing I "lose" 1 usable address given to me by the ISP. I have a /29 or 255.255.255.248 subnet mask which gives me 6 usable addresses. 1 is for the Dialer0 interface to act as the gateway for the remaining 5. If I assign the VLAN1 an address I now only have 4. Maybe what I am trying to do is not possible, but I would think you could some how. Ideas?

 

[Jimtron26]

How many hosts do you have on your internal network? Is there any reason you are assigning public IP addresses to the internal network?

Can you not give the local LAN private addresses from the RFC 1918 ranges and then NAT between the internal network and your external IP address?

eg
internal network = 192.168.0.0/24
ip address vlan1 = 192.168.0.1
ip address dialer0 = <public ip address>
Nat statement=
#ip nat inside source list 1 interface dialer0 overload
ACL=
#access-list l permit ip 192.168.0.0 0.0.0.255

vlan1 #ip nat inside
Dialer0 #ip nat outside

This should do the trick whilst retaining your remaining 5 public addresses

)

 

[bdlamprecht]

I know that using NAT would make this a whole lot easier, but I need to use public IPs on my internal network. There is no way around this. I'm stuck and might have to call somebody and pay $$$ for the support. We shall see. Any further ideas?

 

[DanInRaleigh]

...you could just nat with public ip address pool..
...statically map

http://www.daniel-white.com

 

[helpdeskdan]

I don't see any unnumbered here.... where is it? Shouldn't your config should look like this:

interface Dialer0
ip unnumbered Ethernet0
no ip directed-broadcast
encapsulation ppp
dialer pool 1
dialer-group 1
ect....

 

[bdlamprecht]

You very well may be right. I don't know how to use the unnumbered feature or if that is even what I am looking for. I may try and play with it some more, but if you have any more ideas or hints you could give me that would be helpful. Thanks.

 

[helpdeskdan]

Actually, I have it backwards - good thing I caught that. You should have the ip unnumbered on your ethernet interface pointing to your dialer interface. It would be:

interface FastEthernet0
ip unnumbered Dialer0

Here's info on ip unnumbered - very simple actually.

http://www.cisco.com/warp/public/701/20.html

I've never heard of it used on a dialer int. Should work in theory though - give it a try!