Gigabit uplink port not blinking

Unanswered Question


I have two number of Cisco catalyst 2950T switches, 24 ports with 2 gigabit ports.

Earlier both the gigabit uplinking ports were connected to a Cisco 4507 switch by means of four UTP cables for redundancy.

Recently one of the physical cables was cut and we had to change the network design.

We connected one gigabit port from both the switches (2950T) to the 4507 core . The other gigabit port is cascaded to the gigabit port of the other switch.

While doing so the ports and the cascading is not working. We checked the cable and found nothing wrong with it.(straight CAT 6 UTP cable)

Below is the configuration and output of show interface GigabitEthernet0/2.


interface GigabitEthernet0/1

description "Connected to CORE"

switchport mode trunk


interface GigabitEthernet0/2

description "Cascaded to SWITCH B"


interface GigabitEthernet0/1

description "Connected to CORE"

switchport mode trunk


interface GigabitEthernet0/2

description "Cascaded to SWITCH A"

GigabitEthernet0/2 is down, line protocol is down (notconnect)

Hardware is Gigabit Ethernet, address is 0015.639f.8c9a (bia 0015.639f.8c9a)

Description: " Cascaded to SWITCH B "

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

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

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Auto-duplex, Auto-speed, media type is RJ45

input flow-control is off, output flow-control is off

ARP type: ARPA, ARP Timeout 04:00:00

Last input 5w5d, output 4d21h, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (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

53269980 packets input, 3899309133 bytes, 0 no buffer

Received 53167918 broadcasts (0 multicast)

0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 53137711 multicast, 0 pause input

0 input packets with dribble condition detected

1256838 packets output, 187554610 bytes, 0 underruns

I have also tried switchport mode trunk but without any luck.

However we also do have similar switches connected in the same manner as above and they are functioning perfectly.

Can someone please identify what is wrong and suggest how to make it work



I have this problem too.
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Giuseppe Larosa Sat, 10/18/2008 - 03:46

Hello Vikrant,

you probably have a cable problem:

1000 Mbps over RJ-45 uses all 4 pairs in the cable so a normal FE cross-over cable is not the right cable for the job.

You need a special cable that will exchange wires of the other two pairs too:



---- ! normal cross-over above



--- ! modified cross-over for GE

We had to have some cables made for this purpose to get a switch to switch 802.3ab link working

Hope to help



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