02-07-2018 01:50 AM - edited 03-08-2019 01:44 PM
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 !
02-07-2018 02:02 AM
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
02-07-2018 02:12 AM
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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