Hope someone can help. I am setting up a lab with three Cisco 2500 routers.I am using DCE DTE crossover cables between the routers. On one link I am getting Serial interface up down. I have checked the keep alive settings are both interfaces are set to 10 sec and encapsulation settings are both set to HDLC. I have the clock rate configured on the DCE end (whch is where I get the up down)and I have changed the crossover cable and still no joy. Any ideas?
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Serial interface up line protocol down
- Thread starter bsludick
- Start date
namesrhard2pick
Technical User
I would add clockrate 56000 to your R3 sX interface before swapping cables around. I had a similiar issue and it was corrected by adding a secondary clockrate to my 3rd router. I think dtrtel is on to something.
dtrtel
Technical User
- Jul 18, 2007
- 85
I would add that you can do this really fast because you don't have to worry about re-configuring to pass IP traffic at this point. Just check the interfaces for "line protocol is up" while consoled-in to the router(s).
--jeff
--jeff
- Thread starter
- #23
Hi
I am really confused now. Bearing in mind that the link I am having issues with is from R1/serial 1/DCE to R3/serial 1/DTE.
Router 1 was Up down and Router 3 Up Up.
When I moved the cable from a working link (R1/s0 - R2/s0) on router 1 to (R1 / s1 - R2 / s0)guess what... the Serial 1 interface came up up!!! So I am thinking that it must be the cable. Strange as already replaced the cable with a new one.
So I then move the DTE ends across so we have as before:
Router 1 / serial 1 - Router 3 / serial 1
Router 1 / serial 0 - Router 2 /serial 0
and I get the same old error message again:
Router1#sh ip int brief
Interface IP-Address OK? Method Status Protoco
BRI0 unassigned YES NVRAM administratively down down
BRI0:1 unassigned YES unset administratively down down
BRI0:2 unassigned YES unset administratively down down
Ethernet0 192.168.0.20 YES NVRAM up up
Loopback0 10.1.10.2 YES NVRAM up up
Serial0 10.1.1.2 YES NVRAM up up
Serial1 10.1.2.2 YES NVRAM up down
Router1#
I am really confused now. Bearing in mind that the link I am having issues with is from R1/serial 1/DCE to R3/serial 1/DTE.
Router 1 was Up down and Router 3 Up Up.
When I moved the cable from a working link (R1/s0 - R2/s0) on router 1 to (R1 / s1 - R2 / s0)guess what... the Serial 1 interface came up up!!! So I am thinking that it must be the cable. Strange as already replaced the cable with a new one.
So I then move the DTE ends across so we have as before:
Router 1 / serial 1 - Router 3 / serial 1
Router 1 / serial 0 - Router 2 /serial 0
and I get the same old error message again:
Router1#sh ip int brief
Interface IP-Address OK? Method Status Protoco
BRI0 unassigned YES NVRAM administratively down down
BRI0:1 unassigned YES unset administratively down down
BRI0:2 unassigned YES unset administratively down down
Ethernet0 192.168.0.20 YES NVRAM up up
Loopback0 10.1.10.2 YES NVRAM up up
Serial0 10.1.1.2 YES NVRAM up up
Serial1 10.1.2.2 YES NVRAM up down
Router1#
jneiberger
Technical User
If you have a serial link and one side is up/up while the other is up/down, that's almost certainly a bad cable or interface.
- Thread starter
- #26
This is the third time I am changing the cable and the cable worked fine on the link it took if from - so it cannot be the cable.
The interface (Router1/Serial 1) was up up a minute ago After I plugged router 2's Serial 0 DCE cable into the Router 1 Serial 1 interface.
On a Cisco 2500 with two serial interfaces can you configure both as DCE's?
The interface (Router1/Serial 1) was up up a minute ago After I plugged router 2's Serial 0 DCE cable into the Router 1 Serial 1 interface.
On a Cisco 2500 with two serial interfaces can you configure both as DCE's?
jneiberger
Technical User
Sure, you can have both interfaces as DCE. It doesn't matter. Just make sure your cables are connected to the right interfaces and you have clocking on your DCE. If you're seeing the same thing with different cables then I think you might have a bad interface. Try mixing things up a bit to see if you can isolate a bad interface. I used to have a lab full of 2500 series routers at my house and I went through this then. One of the routers ended up having a bad interface.
jneiberger
Technical User
Just to clarify, the DCE/DTE function as it relates to a frame relay switch is entirely unrelated to the DCE/DTE function at the physical layer. They do not correlate in any way.
dtrtel
Technical User
- Jul 18, 2007
- 85
<quote>When I moved the cable from a working link (R1/s0 - R2/s0) on router 1 to (R1 / s1 - R2 / s0)guess what... the Serial 1 interface came up up!!! </quote>
STOP! You just proved that R1(s1) is good.
Now you turn your attention to R3(s1). You need to be systematic and take good notes. You need to prove this interface is bad. Connect R3(s1) to any other known good serial port. Check which cable end (DTE or DCE) is connected to which serial port and check the running-config to be sure you set the clockrate on the DCE cabled int. It won't hurt to set a clockrate on a DTE interface, but it DOES matter if you don't set the clockrate on the DCE interface.
<quote>So I am thinking that it must be the cable. Strange as already replaced the cable with a new one. </quote>
WAIT! Premature assumption. If you are certain that it should work as connected and configured, then you can swap the cable with a cable you know works on the other connections.
--jeff
STOP! You just proved that R1(s1) is good.
Now you turn your attention to R3(s1). You need to be systematic and take good notes. You need to prove this interface is bad. Connect R3(s1) to any other known good serial port. Check which cable end (DTE or DCE) is connected to which serial port and check the running-config to be sure you set the clockrate on the DCE cabled int. It won't hurt to set a clockrate on a DTE interface, but it DOES matter if you don't set the clockrate on the DCE interface.
<quote>So I am thinking that it must be the cable. Strange as already replaced the cable with a new one. </quote>
WAIT! Premature assumption. If you are certain that it should work as connected and configured, then you can swap the cable with a cable you know works on the other connections.
--jeff
No..It seems as though dtrtel believes there is a possible issue with R3, as bsludick has already proved the cabling to be good, plus the serial port came up briefly on R1.
As namesrhard2pick suggested earlier, it may be an idea to provide clocking from R3 > R1, as you may have a dodgey port as some of the guys have tried to outline..
Best of luck
As namesrhard2pick suggested earlier, it may be an idea to provide clocking from R3 > R1, as you may have a dodgey port as some of the guys have tried to outline..
Best of luck
- Thread starter
- #34
burtsbees,
Don't worry so am I...
R1 S1 to R3 S1, R1=DCE and R3=DTE, R1 with clock rate and R3 with none...does not work with any cable.
R1 S1 to R3 S1, R1=DTE and R3=DCE, clock on R3...have not tried this yet, will do so this evening and let you know.
Thanks
Don't worry so am I...
R1 S1 to R3 S1, R1=DCE and R3=DTE, R1 with clock rate and R3 with none...does not work with any cable.
R1 S1 to R3 S1, R1=DTE and R3=DCE, clock on R3...have not tried this yet, will do so this evening and let you know.
Thanks
Cool---just wanted to clarify for dtrtel...
"STOP! You just proved that R1(s1) is good."
No---you have probably proven the contrary to that, actually. Okay---please get back when you do try the second one! Also, here's a frame-relay config, if you decide to also try that...
!
version 11.3
service telnet-zeroidle
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Frame_Switch
!
enable password xxxxxx
!
frame-relay switching
!
!
interface Ethernet0
ip address 172.16.0.2 255.255.0.0
!
interface Serial0
no ip address
encapsulation frame-relay
no ip mroute-cache
clockrate 4000000
frame-relay lmi-type ansi
frame-relay intf-type dce
frame-relay route 101 interface Serial1 102
!
interface Serial1
no ip address
encapsulation frame-relay
clockrate 4000000
frame-relay intf-type dce
frame-relay route 102 interface Serial0 101
!
interface BRI0
no ip address
shutdown
!
ip classless
!
!
line con 0
password xxxxxxxx
logging synchronous
login
line aux 0
line vty 0 4
password xxxxxxxx
login
!
end
Serial 0 goes to dlci 101, and serial 1 goes to dlci 102...
Burt
"STOP! You just proved that R1(s1) is good."
No---you have probably proven the contrary to that, actually. Okay---please get back when you do try the second one! Also, here's a frame-relay config, if you decide to also try that...
!
version 11.3
service telnet-zeroidle
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Frame_Switch
!
enable password xxxxxx
!
frame-relay switching
!
!
interface Ethernet0
ip address 172.16.0.2 255.255.0.0
!
interface Serial0
no ip address
encapsulation frame-relay
no ip mroute-cache
clockrate 4000000
frame-relay lmi-type ansi
frame-relay intf-type dce
frame-relay route 101 interface Serial1 102
!
interface Serial1
no ip address
encapsulation frame-relay
clockrate 4000000
frame-relay intf-type dce
frame-relay route 102 interface Serial0 101
!
interface BRI0
no ip address
shutdown
!
ip classless
!
!
line con 0
password xxxxxxxx
logging synchronous
login
line aux 0
line vty 0 4
password xxxxxxxx
login
!
end
Serial 0 goes to dlci 101, and serial 1 goes to dlci 102...
Burt
dtrtel
Technical User
- Jul 18, 2007
- 85
<quote>
Now I'M confused!
R1 S1 to R3 S1, R1=DCE and R3=DTE, R1 with clock rate and R3 with none...does this work with ANY cable?
R1 S1 to R3 S1, R1=DTE and R3=DCE, clock on R3...does this work with ANY cable?
</quote>
Good points, Burt. I was partially premature in stating that R1(s1) is good because I did not indicate conditionally that the DCE role hadn't changed for R1(s1) when it came up on R2(s0). But if R1(s1) was configed and connected as the DCE then, I stand by this conclusion.
--jeff
Now I'M confused!
R1 S1 to R3 S1, R1=DCE and R3=DTE, R1 with clock rate and R3 with none...does this work with ANY cable?
R1 S1 to R3 S1, R1=DTE and R3=DCE, clock on R3...does this work with ANY cable?
</quote>
Good points, Burt. I was partially premature in stating that R1(s1) is good because I did not indicate conditionally that the DCE role hadn't changed for R1(s1) when it came up on R2(s0). But if R1(s1) was configed and connected as the DCE then, I stand by this conclusion.
--jeff
namesrhard2pick
Technical User
Could it be a layer 2 issue since the protocol status is down? I noticed when looking more closely at the running configs for r1 and r3, the statements "no ip route-cache"
"no ip mroute-cache" are missing from r1 s1. These two statements are on the r3 s1 interface. If I am totally off, an explanation of these statements will be great.
"no ip mroute-cache" are missing from r1 s1. These two statements are on the r3 s1 interface. If I am totally off, an explanation of these statements will be great.
jneiberger
Technical User
This has nothing to do with route caching (fast switching), which is what those statements affect. Do a web search for Cisco fast switching to read more about that topic. The short version of the story is that it lessens the load on the router by caching previous routing decisions so the routing portion of the router doesn't have to work so hard.
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