Rich, how does Ethernet "carrier-sense mechanism" differ from "link integrity check"? I mean aren't those two the same? A quote from O'Reilly:
<<<<< 100BASE-TX link integrity test The 100BASE-TX transceiver circuits (PHY) continually monitor the receive data path for activity as a means of checking that the link is working correctly. The signal encoding on 100BASE-TX segments sends signals continually, even during idle periods. Therefore, activity on the receive path is sufficient to provide a continual check of link integrity. >>>>> As I understand, in case of "Link Integrity Check"(physical layer signals) fails, the switch/router shows "line protocol is down (notconnect)".. regards, martin 2011/8/2 Rich Davies <[email protected]>: > I would think the switchport utilizes its carrier-sense mechanism (part of > CSMA/CD) to see if port is in a carrier-sense state (physical connection > layer 1). As for the ethernet frames acting as a keepalive I am guessing > this is a layer 2 checksum as the ethernet frames are layer 2 whereas your > carrier sense is layer 1. > > Rich > > > 2011/7/30 Martin T <[email protected]> >> >> I made a following connection: >> >> T60[eth0] <-> [Fa0/2]WS-C2950C-24 >> >> >> The connection is fine: >> >> WS-C2950C-24#show interfaces Fa0/2 status >> >> Port Name Status Vlan Duplex Speed Type >> Fa0/2 -> T60 connected 1 a-full a-100 >> 10/100BaseTX >> WS-C2950C-24# >> >> >> ..and at the very moment I remove the cable either from the T60 or the >> switch, the "line protocol" in the switch will be down. Even if I >> apply following configuration to a switch port: >> >> WS-C2950C-24#sh run int Fa0/2 >> Building configuration... >> >> Current configuration : 163 bytes >> ! >> interface FastEthernet0/2 >> description -> T60 >> switchport mode access >> switchport nonegotiate >> no keepalive !keepalive frames are disabled >> no cdp enable >> spanning-tree bpdufilter enable >> end >> >> WS-C2950C-24# >> >> ..the line protocol of the switch port is down immediately if I >> disconnect the cable either from the laptop or the switch. So as far >> as I understand, keepalive frames have nothing to do with "line >> protocol". "line protocol" status should depend on "link integrity >> test" which means that port circuit continually sends signals- even >> during the idle periods where there isn't any traffic on the network. >> "link integrity test" can not be configured under software. According >> to O'Reilly "Ethernet" this should apply to 10BASE-T, 100BASE-TX as >> well as 1000BASE-T. >> Anyone has an other opinion? Or confirm this? :) >> >> >> regards, >> martin >> >> 2011/7/28 Scott Granados <[email protected]>: >> > 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 >> >> _______________________________________________ >> >> cisco-nsp mailing list [email protected] >> >> https://puck.nether.net/mailman/listinfo/cisco-nsp >> >> archive at http://puck.nether.net/pipermail/cisco-nsp/ >> >> >> > >> > _______________________________________________ >> > cisco-nsp mailing list [email protected] >> > https://puck.nether.net/mailman/listinfo/cisco-nsp >> > archive at http://puck.nether.net/pipermail/cisco-nsp/ >> > >> >> _______________________________________________ >> cisco-nsp mailing list [email protected] >> https://puck.nether.net/mailman/listinfo/cisco-nsp >> archive at http://puck.nether.net/pipermail/cisco-nsp/ > > _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
