Cisco 878 Router in G.SHDSL Config

Answered Question
Sep 3rd, 2008

I want to use 2 Cisco 878 routers to extend my LAn to a location where I have copper only. I know I can use the G.SHDSL port in back to back configuration but don't know how to set it up.

CAn anyone help me


Mike Williams

Correct Answer by andrew.prince@m... about 8 years 5 months ago

The cable specs are here:-

70% down the page, then just cross pins 3 & 4 at one end.


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Overall Rating: 5 (1 ratings)
michael.m.williams Wed, 09/03/2008 - 08:52


based on this the setting for the port are set to auto config. The connection is RJ-11 on the back of the 878, would you know how to make 2 878 talk over the G.SHDSL port. It comes with a purple RJ-11 ccable, but van't find the pinouts anywhere. This is new tech for me.


michael.m.williams Fri, 09/05/2008 - 09:12


I now have the two 878 connected and I get a CD LED, and I see both atm0 and dsl are up. here is the problem.

When I am consoled in I can telnet or ping both routers. Router one is connected via FE0 to network, I can ping and telnet to both ATM and VLAN interfaces on router 1, but I can not see ATM0 or VLAn interface on router 2. I have enabled EIGRP and inputted static routes but still can not talk or pass data.

Any ideas?


michael.m.williams Fri, 09/05/2008 - 10:26

Here are the configs.

ITSCR3SRK2 is connected to my network on fa 1

and connected to STDTBRT01 via the ATMO (G.SHDSL) port. Like I said when I am consoled in to ITSCR3RT01 I can ping on the STDTBRT01. I also tried to do a show ip eigrp neighbor on STDTBRT01 but it didn't see the other router.



andrew.prince@m... Fri, 09/05/2008 - 12:19


Can you post the output on both routers:-

show ip eigrp nei

show ip eigrp interface

show ip eigrp topology

andrew.prince@m... Sat, 09/06/2008 - 02:14

Looks like the routers do not like passing the EIGRP multicast frames over the SDSL. I think you have 2 options:-

1) Create GRE tunnels, and encapsulate EIGRP into the tunnel over the SDSL.

2)Only use the ATM interfaces for the layer2 connectivity - and use the dialer interface for all IP communications encapsulating into PPP.


michael.m.williams Mon, 09/08/2008 - 06:34

I got a step closer and can now talk to the ATM interface on the remote router.

I turned on debug ATM error and notice I was getting an "Encapsulation error1, link=7, host xxxxx"

So I found that I needed to add the broadcast command under interface ATM0

PVC 8/35

protocol ip broadcast. This now is allowing me to ping the interface on remote router and router are exchanging hello packets and seeing eachother, now I am trying to pass Vlans and set up the management vlan in vlan 50, set up VTP domians on both routers but I can not talk to the management IP on the remote router. I have configured a vlan trunk on port fa 3 of the local router. I can not talk to the management side of the remote router.


andrew.prince@m... Mon, 09/08/2008 - 07:50


You are tyring to pass layer 2 information over a layer 3 link, that is not IEEE 802.3 - this you cannot do.

If you want to "route" between the VLAN's at the two seperate ends - you need a layer 3 interface for inter-vlan routing.

See the below links:-



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