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I just bought a Cisco 3750X switch and when I did a sh ip int brief command, I see that my TE1/1/1 interface (it's a 10G port) has status up but protocol down.

Right now, this 10G port is connected to a NIC in a PC, but there is no traffic going in or out. Is this "status up/protocol down" normal? What does the "protocol" mean?

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3 Answers 3

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Protocol refers to "Line Protocol", which is a Cisco way of saying "the connection". Basically, up/down means the port is available for a cable/connection, but doesn't have one. Check the cable, or other computer.

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This might be a very late reply but here's what I understood so far: The interface status has two parts to it:

  1. the interface up or down
  2. the line protocol up or down.

The interface up status is determined by testing checking for the carrier signal coming across the interface.

The line protocol up status is when the router receives the keep-alive messages across the interface. Every device connected sends across heart-beat messages or keep-alive messages to indicate that they are still available. If the recipient router does not receive the keep-alive messages for a while (a hold-down time), the status is set to line protocol down.

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Protocol Status refers generally two the layer to status. It is always down if the Line status is down. if the Line status is up,a protocol status of down usually is caused by mismatched data link layer configuration For an example serial interfaces has their combination when one router has configured to use PPP(Point_to_Point Protocol) and other remains the default HDLC (Higher_level Data Link Control) configuration and this will cause to display as "Line status Up Protocol Down" .

  • Before Configure one router to PPP (Default is HDLC)

R1#show interfaces serial 1/0

Serial1/0 is up, line protocol is up (connected) Hardware is HD64570 MTU 1500 bytes, BW 128 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set, keepalive set (10 sec)

R2#show interfaces se1/0

*Serial1/0 is up, line protocol is up (connected)* Hardware is HD64570 MTU 1500 bytes, BW 128 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set, keepalive set (10 sec)

  • After configuring R1 as PPP

R1#show interfaces serial 1/0

Serial1/0 is up, line protocol is down (disabled) Hardware is HD64570 MTU 1500 bytes, BW 128 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation PPP, loopback not set, keepalive set (10 sec)

R2#show interfaces serial 1/0

Serial1/0 is up, line protocol is down (disabled) Hardware is HD64570 MTU 1500 bytes, BW 128 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set, keepalive set (10 sec)

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