[c-nsp] Are "line protocol" and LIT the same?

[Scott Granados]

There are more measured than simple keep alives.  If you pull an interface 
you lose carrier, timing, frames, and other various components of the 
communication method in question.

When you view an interface the first up indicates that the interface is 
enabled and the line protocol means that in a down state you're not 
receiving anything valid in terms of your communications protocol of choice.


-----Original Message----- 
From: Martin T
Sent: Wednesday, July 27, 2011 7:37 PM
To: Lukasz Bromirski
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Are "line protocol" and LIT the same?

Lukasz,
it looks like the default value for keepalive packet is 10s. However,
if I disconnect the other end from my switch port, the line protocol
will be down immediately. How to explain this? In addition, there are
interfaces, which by default don't have keepaive set(for example
WS-C3750G-24TS SFP interfaces). They have "Keepalive not set" under
"show interfaces" output. However, they still have "line protocol is
up (connected)".. How to explain this?


regards,
martin


2011/4/26 Lukasz Bromirski <lukasz at bromirski.net>:
> On 2011-04-26 01:11, Martin T wrote:
>>
>> When Cisco switch or router port is "connected", it has status "line
>> protocol is up". As far as I know, this applies to all interface
>> types(10BASE-T, 100BASE-TX, 1000BASE-T, 1000BASE-LX10, 1000BASE-SX etc
>> with different transceivers).
>> What is this "line protocol"? I always thought "line protocol" is up
>> once any electrical pulses are detected by Rx. Or is "line protocol"
>> strictly "link integrity test"(LIT) pulses(100-200ns of electrical
>> pulses with 16ms+/-8ms interval)? Any clarification would be much
>> appreciated.
>
> "Line protocol" for Ethernet interfaces is Ethernet frame. Cisco boxes
> send Ethernet keepalive frame and when it doesn't loop back, they
> declare line protocol down:
>
> http://www.cisco.com/en/US/docs/ios/12_3/interface/command/reference/int_i1g.html#wp1154231
>
> --
> "There's no sense in being precise when |               Łukasz Bromirski
>  you don't know what you're talking     |      jid:lbromirski at jabber.org
>  about."               John von Neumann |    http://lukasz.bromirski.net
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