CSU to CSU direct connection

dhopper82 · ‎01-05-2009

I am working on a project for our wan. I have a lab set up and I am trying to connect 2 routers up via frame-relay and am having some issues. I connected the 2 up using a CAT-5 T1 cable (pins 1-4, 2-5). That is the only physical connection between the two. On the CSU's I get a green CD light. My primary router is configured like this on it's serial interface and sub-int...

interface Serial0/0

description T3#1-10QIDA500046SC

mtu 4400

no ip address

encapsulation frame-relay

ip route-cache flow

no ip mroute-cache

no fair-queue

frame-relay lmi-type ansi

!

interface Serial0/0.1 point-to-point

description PPVC SC100

bandwidth 128

ip address 10.35.151.1 255.255.255.0

traffic-shape rate 128000 7936 7936 1000

traffic-shape adaptive 96000

frame-relay class primary

frame-relay interface-dlci 476

!

My "WAN" router is set up as the following...

interface Serial0/0

no ip address

encapsulation frame-relay

no ip mroute-cache

no fair-queue

service-module t1 timeslots 1-2

service-module t1 remote-alarm-enable

frame-relay lmi-type ansi

!

interface Serial0/0.1 point-to-point

description SC100

ip address 10.35.151.2 255.255.255.0

frame-relay class primary

frame-relay interface-dlci 476

!

When I connect the 2 up the serial interface comes up but the sub shows down/down. I can never ping the ip addresses. Eventually the line protocol dies on the serial interface. It looks like the LMI is connecting somewhat because when I do a show int it gives me this...

Serial0/0 is up, line protocol is down

Hardware is PQUICC with Fractional T1 CSU/DSU

MTU 1500 bytes, BW 128 Kbit, DLY 20000 usec,

reliability 203/255, txload 1/255, rxload 1/255

Encapsulation FRAME-RELAY, loopback not set

Keepalive set (10 sec)

LMI enq sent 118, LMI stat recvd 0, LMI upd recvd 0, DTE LMI down

LMI enq recvd 61, LMI stat sent 0, LMI upd sent 0

LMI DLCI 0 LMI type is ANSI Annex D frame relay DTE

Broadcast queue 0/64, broadcasts sent/dropped 1/0, interface broadcasts 0

Last input 00:09:51, output 00:00:00, output hang never

Last clearing of "show interface" counters 00:20:10

Input queue: 0/75/8/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

88 packets input, 1151 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

55 input errors, 21 CRC, 33 frame, 0 overrun, 0 ignored, 1 abort

148 packets output, 2254 bytes, 0 underruns

0 output errors, 0 collisions, 37 interface resets

0 output buffer failures, 0 output buffers swapped out

5 carrier transitions

DCD=up DSR=up DTR=up RTS=up CTS=up

One more thing. My frame-relay map-class command for the primary class is set like this...

map-class frame-relay primary

frame-relay end-to-end keepalive mode bidirectional

As far as I can tell, the configs should work. What am I missing? Is it the cable?

Richard Burts · ‎01-05-2009

Dennis

What you are missing is a Frame Relay switch. You have configured the two routers for normal Frame Relay connectivity. But the normal Frame Relay configuration which you have done is based on connection to a Frame Relay switch.

To resolve this you could either put the serial connections to a third router which you could configure as a Frame Relay switch or you could keep the connection back to back and modify the interface configuration.

Also I believe that you have an issue about this back to back connection in terms of what is providing clocking. There are parts of the configuration which you have not shown us, but from what you have posted it looks like both routers are taking the defaults which is to get clocking from the line. But in a back to back connection there is no clock signal on the line unless one of the routers is configured to use line clocking source internal.

HTH

Rick

HTH

Rick

dhopper82 · ‎01-05-2009

Thanks Rick! Besides the clock rate command on the serial interface of one of the routers would there be any other commands I would have to add??

Giuseppe Larosa · ‎01-05-2009

Hello Dennis,

on the WAN router you should configure it to behave like a FR switch port

frame-relay switching

int ser0/0

! this makes the inteface behave like a FR switch port

frame-rel intf-type dce

These are just suggestions the theory behind has been well explained by Rick

About clock you say you have a CSU device but I don't know if it can provide clock on both sides of connection or it is expecting to receive it on the Service provider side.

hope to help

Giuseppe

Richard Burts · ‎01-05-2009

Dennis

It is difficult to tell from what is posted so far what kind of CSU is on the first router. Pretty obviously the second (WAN) router has an integrated/internal CSU which uses the service module commands. I believe that on one of the routers (and based on what we see so far I would suggest on the WAN router) you would want to configure clock source internal (the precise syntax may vary depending on the card type). You only need to specify clock source on one of the routers.

[edit] it is hard to tell from the original post whether the cable being used is a traditional (straight through) or is a cross over cable. For back to back connection you need a cross over T1 cable.

HTH

Rick

HTH

Rick