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unusual behavior of cdp neighbor when ws-2950 connect to ws-2960 via juniper EX2200

we have a physical topology with ws-2950 connect to juniper ex2200 and some cisco device connect to ex2200 via a optical link.

sw-01, sw-02, c1841,sw-03 <--via optical link -->Ge-0/0/0 | EX2200| Ge-0/0/23<--via rj45-->G0/2| ws-2950.

EX2200 - Ge-0/0/0 config as access port, access vlan 55

EX2200 - Ge-0/0/23 config as trunk port, native vlan 1

ws-2950 - G0/3 config as trunk port

But when "show cdp neighbor" in ws-2950, we see sw-01, sw-02, c1841,sw-03 as direct neighbor.

 

Vlan1                      10.x.y.6     YES manual up                    up
GigabitEthernet0/2         unassigned      YES unset  up                    up
Port-channel1              unassigned      YES unset  up                    up



SW-01      Gig 0/2            149          S I      WS-C2960-2Fas 0/18
SW-02    Gig 0/2            155          S I      WS-C2960-2Fas 0/15
C1841-1  Gig 0/2            125         R S I     Cisco 1841Fas 0/1
SW-04
                 Gig 0/2            137          S I      WS-C2950T-Fas 0/48

				 
juniper@EX2200>
21:31:15: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up
21:31:16: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to upexit


[Connection to 10.46.224.5 closed by foreign host]
SW-2950-local#show c
21:31:22: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet0/2 (1), with SW-01 FastEthernet0/18 (2248).dp nei de
-------------------------
Device ID: SW-01
Entry address(es):
  IP address: 10.x.y.254
Platform: cisco WS-C2960-24TT-L,  Capabilities: Switch IGMP
Interface: GigabitEthernet0/2,  Port ID (outgoing port): FastEthernet0/18
Holdtime : 177 sec

Version :
Cisco IOS Software, C2960 Software (C2960-LANBASEK9-M), Version 12.2(44)SE6, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Mon 09-Mar-09 18:10 by gereddy

advertisement version: 2
Protocol Hello:  OUI=0x00000C, Protocol ID=0x0112; payload len=27, value=00000000FFFFFFFF010220FF0000000000003037A6565E00FF0000
VTP Management Domain: ''
Native VLAN: 2248 (Mismatch)
Duplex: full
Management address(es):
  IP address: 10.x.y.254

-------------------------
Device ID: SW-02
Entry address(es):
  IP address: 10.x.y.6
Platform: cisco WS-C2960-24TT-L,  Capabilities: Switch IGMP
Interface: GigabitEthernet0/2,  Port ID (outgoing port): FastEthernet0/15
Holdtime : 120 sec

Version :
Cisco IOS Software, C2960 Software (C2960-LANBASEK9-M), Version 12.2(55)SE7, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2013 by Cisco Systems, Inc.
Compiled Mon 28-Jan-13 10:22 by prod_rel_team

advertisement version: 2
Protocol Hello:  OUI=0x00000C, Protocol ID=0x0112; payload len=27, value=00000000FFFFFFFF010220FF0000000000007C95F3DD1C00FF0000
VTP Management Domain: ''
Native VLAN: 50 (Mismatch)
Duplex: full
Management address(es):
  IP address: 10.x.y.6

-------------------------
Device ID: C1841-1
Entry address(es):
  IP address: 172.x.k.178
Platform: Cisco 1841,  Capabilities: Router Switch IGMP
Interface: GigabitEthernet0/2,  Port ID (outgoing port): FastEthernet0/1
Holdtime : 147 sec

Version :
Cisco IOS Software, 1841 Software (C1841-IPBASE-M), Version 12.4(1c), RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2005 by Cisco Systems, Inc.
Compiled Tue 25-Oct-05 17:10 by evmiller

advertisement version: 2
VTP Management Domain: ''
Duplex: full
Management address(es):

-------------------------
Device ID: SW-04
Entry address(es):
  IP address: 10.x.y.3
Platform: cisco WS-C2950T-48-SI,  Capabilities: Switch IGMP
Interface: GigabitEthernet0/2,  Port ID (outgoing port): FastEthernet0/48
Holdtime : 158 sec

Version :
Cisco Internetwork Operating System Software
IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(14)AZ, RELEASE SOFTWARE (fc2)
Copyright (c) 1986-2003 by cisco Systems, Inc.
Compiled Tue 14-Oct-03 17:30 by antonino

advertisement version: 2
Protocol Hello:  OUI=0x00000C, Protocol ID=0x0112; payload len=27, value=00000000FFFFFFFF010220FF000000000000000E84478440FF0000
VTP Management Domain: ''
Duplex: full
			

It confused me.

 

Anybody has an explanation for this plz !

 

 

Everyone's tags (3)
2 REPLIES 2
Participant

Re: unusual behavior of cdp neighbor when ws-2950 connect to ws-2960 via juniper EX2200

Hi,

 

I have observed this same behaviour before with Juniper EX switches as they forward CDP messages to 01:00:0c:cc:cc:cc between interfaces which generates erroneous CDP duplex mismatch alerts. I believe that you can configure the Juniper EX switch to filter CDP messages to stop this behaviour if required

 

Will

Collaborator

Re: unusual behavior of cdp neighbor when ws-2950 connect to ws-2960 via juniper EX2200

Hi,

Juniper switches have a feature called "CDP passthrough". A juniper switch, by default,  will forward  cdp packets  in ethernet frames.

This is way you are seeing the devices on the other end of the juniper ex switch.

 

Thanks

John

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