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: [email protected]
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 <[email protected]>:
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:[email protected]
about." John von Neumann | http://lukasz.bromirski.net
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