Hi ,
Procedure for hard loopback test.
If you want to check that your hardware works ok or not, you can perform a hardware
loopback test. Here are the instructions for conducting a HARD loopback test for a CSU/DSU
connected to a Cisco Systems Router.
Step 1: Create T1/E1 loopback plug
- Take a working straight through RJ-45 cable (as short as possible)
- Using wire cutters, cut the cable so there's about 5" of cable and the
RJ-45 head
- The pins on an RJ-45 cable plug are numbered from 1 through 8. With the
metal pins of the plug facing toward you, pin 1 is the leftmost pin.
- Take the exposed wires corresponding to pins 1 & 4 strip them, then twist
them together
- Do the same for pins 2 & 5
- Leave the rest of the wires alone
Step 2: Install the loopback plug
- Remove the T1/E1 (RJ-45) Connector from the Network port of the CSU/DSU
- Plug the loopback plug into the same port you just removed T1/E1 cable from
Step 3: Save your router configuration
- Enter enable mode: enable
- Use the cmd: write mem
Step 4: Set the encapsulation to HDLC (Cisco Routers will only PROPERLY loop
in HDLC)
- Enter config terminal mode: config term
- Enter the interface config mode: interface serial [your T1/E1 interface #]
- Issue the cmd: encap HDLC
- Clock source should be internal
- Exit config terminal mode: Ctrl + Z
Step 5: Set an IP Address (ONLY IF YOU DON'T HAVE AN IP ON THE MAIN
INTERFACE ALREADY)
- Issue the cmd: sh run
- Is there an IP address under your T1/E1's MAIN (physical) interface?
- If YES, then skip to STEP 6
- If NO, then continue with STEP 5
- Enter config terminal mode: config term
- Enter the interface config mode: interface serial [your T1/E1 interface #]
- Issue the cmd: ip address 10.13.13.13 255.255.255.0
* MAKE SURE THIS ADDRESS DOESN'T OVERLAP WITH ANY OF YOUR OTHER NETWORKS
- If it overlaps, use any other free address & a netmask of 255.255.255.0
- Exit config terminal mode: Ctrl + Z
Step 6: Clear Counters
- Type: clear counters
- Press ENTER a couple of times
Step 7: Perform Extended Pings
- Type: ping ip
- Target address = IP of the local T1/E1 int. (the int. you just configured
HDLC on)
- Repeat count = 50
- Datagram size = 1500
- Timeout = press ENTER
- Extended cmds = yes
- Source Address = press ENTER
- Type of service = press ENTER
- Set Df bit in ip header = press ENTER
- Validate reply data = press ENTER
- Data pattern: 0x0000 (all zeros)
- Press ENTER 3 times
Step 8: Perform additional extended pings with different data patters
- Repeat step 7, but use a DATA PATTERN of 0x1111
- Repeat step 7, but use a DATA PATTERN of 0xffff
- Repeat step 7, but use a DATA PATTERN of 0xaaaa
Step 9: Verify results
- All of the above pings should have been 100% successful
- Type: show interface serial [your T1/E1 interface #]
- Your T1/E1 serial interface should have no crc, frame, input, etc. errors
* 5th & 6th lines from the bottom of the show interface cmd output
* If all pings are 100% successful and there are no errors, then your router
should be good, and this is either a
cabling or telco issue.
Step 10: Return router to original state
- Remove loopback plug from the CSU/DSU and replace the T1/E1 cable back in
network port
- On the router, type: copy start run
I couldn't able to attach a link without CCO.
Hope it helps you.
Thanks,
satish
