Trunking between Cisco 3500XL and 3Com 4800g

knichel67 · ‎10-15-2012

I know this is not a 3com support forum, but am hoping that the Cisco GuRu's are watching. I teach the Cisco Network Academy. Our IT Staff recently upgraded the network infrastructure and changed our switches to 3com 4800g's (about 2 years ago).

I want to add a lab bench in my classroom that can access the school's network. My classroom is on a dedicated Cable Modem connection.

Here is my problem...

I am trying to trunk between a 3Com 4800g and a Cisco 3500xl. I can get the a PC that connects to a vlan 1 port on thecisco switch to connect to the 3com switch and get connectivity. However, I cannot get anthing on the cisco switch that is on vlan 2 to connect and get dhcp. I am not a 3com guy, so I am not familiar with the command and configs.

We have 2 vlans on both switches: Vlan 1 is Admin and Vlan 2 is Student.

Our Topology is like this...

Internet -> 3Com 4800g -> Cisco 3500xl

My Cisco 3500xl Fa0/1 is my trunk

interface FastEthernet0/1
 switchport trunk encapsulation dot1q
 switchport mode trunk

The Cisco switch has Vlan 1 interface with appropriate ip in appropriate subnet. I can ping addresses in both vlans from the cisco switch (vlan 1 and vlan 2)

My 3Com 4800g gi1/0/11 is my trunk on other end.

interface GigabitEthernet1/0/11
 port link-type trunk
 port trunk permit vlan 1 to 2
 undo voice vlan mode auto
 broadcast-suppression pps 3000
 undo jumboframe enable
 lldp compliance admin-status cdp txrx

I am connected between them with a crossover cable.

If I plug a pc into the 3500xl to a port in vlan 1, I get DHCP address and connectivity. If I plug into a port in vlan 2, I do not. If I set the pc to have an IP in the vlan 2 subnet, I still have no connectivity. I am guessing there is an issue with the vlan tagging?

This is really bugging me. Any help would be appreciated.

amikat · ‎10-17-2012

Hi,

Will you please post the "sh int fa 0/1 sw" (Cisco) and "display interface gigabitethernet 1/0/11" (3Com) command outputs.

Thanks & Regards,

Antonin

knichel67 · ‎10-17-2012

Thank you for your assistance... I have tried many things and have attempted to reset back to what I "Think" it should be. Here is my best gues.

"sh int fa0/1 sw" :

Name: Fa0/1

Switchport: Enabled

Administrative mode: trunk

Operational Mode: trunk

Administrative Trunking Encapsulation: dot1q

Operational Trunking Encapsulation: dot1q

Negotiation of Trunking: Disabled

Access Mode VLAN: 0 ((Inactive))

Trunking Native Mode VLAN: 1 (default)

Trunking VLANs Enabled: ALL

Trunking VLANs Active: 1,2

Pruning VLANs Enabled: 2-1001

"display interface gigabitethernet 1/0/11":

GigabitEthernet1/0/11 current state: UP

IP Packet Frame Type: PKTFMT_ETHNT_2, Hardware Address: 4001-c6ee-084b

Description: GigabitEthernet1/0/11 Interface

Loopback is not set

Media type is twisted pair

Port hardware type is 1000_BASE_T

100Mbps-speed mode, full-duplex mode

Link speed type is autonegotiation, link duplex type is autonegotiation

Flow-control is not enabled

The Maximum Frame Length is 1522

Broadcast MAX-pps: 3000

Unicast MAX-ratio: 100%

Multicast MAX-ratio: 100%

Forbid jumbo frame to pass

PVID: 1

Mdi type: auto

Link delay is 0(sec)

Port link-type: trunk

VLAN passing : 1(default vlan), 2-3, 666

VLAN permitted: 1(default vlan), 2-4094

Trunk port encapsulation: IEEE 802.1q

Port priority: 0

Peak value of input: 27458267 bytes/sec, at 2000-07-22 06:09:03

Peak value of output: 628684 bytes/sec, at 2000-07-22 08:41:20

Last 300 seconds input: 0 packets/sec 0 bytes/sec 0%

Last 300 seconds output: 4 packets/sec 470 bytes/sec 0%

Input (total): 35659339 packets, 14093307429 bytes

35413010 unicasts, 112462 broadcasts, 133833 multicasts

Input (normal): 35659305 packets, - bytes

35413010 unicasts, 112462 broadcasts, 133833 multicasts

Input: 34 input errors, 0 runts, 0 giants, 0 throttles

14 CRC, 14 frame, - overruns, 6 aborts

- ignored, - parity errors

Output (total): 131102370 packets, 175700831118 bytes

121312651 unicasts, 6268491 broadcasts, 3521228 multicasts, 0 pauses

Output (normal): 131102370 packets, - bytes

121312651 unicasts, 6268491 broadcasts, 3521228 multicasts, 0 pauses

Output: 0 output errors, - underruns, - buffer failures

0 aborts, 0 deferred, 0 collisions, 0 late collisions

0 lost carrier, - no carrier

A standard "student port" on the 3com is configured as follows:

port link-type hybrid

undo port hybrid vlan 1

port hybrid vlan 666 tagged

port hybrid vlan 2 untagged

port hybrid pvid vlan 2

undo voice vlan mode auto

voice vlan 666 enable

mac-vlan enable

broadcast-suppression pps 3000

undo jumboframe enable

poe enable

stp edged-port enable

lldp compliance admin-status cdp txrx

qos trust dscp

A standard "student port" on the 3500xl is configured as follows:

interface FastEthernet0/2

switchport access vlan 2

amikat · ‎10-17-2012

Hi,

Thanks for the reply. It looks that the trunk between Cisco and 3Com is set up OK and both VLANs (1&2) are active (passing). There are some discrepancies between your original post and the current one (like originally only the VLANs 1 & 2 were permitted in trunk, now all seem to be permitted) - I understand that you have made some changes since. What is the VLAN 3 used for?

What concerns me at the moment is the fact that you have also MAC-based VLANs (dynamic in Cisco terminology) enabled at the 3Com box and these always take precedence over port based VLANs. Can you please check with the author of 3Com box configuration the idea and also MAC-to-VLAN mappings ("mac-vlan mac-address ... " command).

Also am I right to understand (from your original post) that you are able to ping from the 3500XL box the "student" workstation connected to VLAN 2 (or at least the VLAN 2 interface at 3Com box)?

Best regards,

Antonin

knichel67 · ‎10-17-2012

Thanks. I have set the permit all to eliminate any problems. I realize that I only need to permit vlan 1 & 2. Vlan 3 is used for a video conferencing room we have and does not need to propogate to my cisco 3500xl. vlan 666 is used for VoIP and also does not need to propogate to my cisco 3500xl. I am only looking to extend vlan 2 into my room so my students can work on computers from the building and access all the resources they will need from my school's network (ie Microsoft Image Deployment...). The switch should be on vlan 1 for management purposes.

I can ping from my 3500xl to a device on vlan 2 that is attached to the 3com switch, but that is because the 3500 and the 3com switches are on vlan 1 and we have acl's that allow vlan 1 to get to vlan 2.

The main problem is that a port from the 3500xl on vlan 2 does not receive a dhcp address like a port on the 3com switch would.

The mac vlans are for VOIP as I understand it...

voice vlan mac-address 0007-0e00-0000 mask ffff-ff00-0000 description 7941

mac-vlan mac-address 0007-0e00-0000 mask ffff-ff00-0000 vlan 666 priority 0

amikat · ‎10-17-2012

Hi,

Thanks for the reply, that makes sense.

Just to separate possible dhcp issue form the vlan&trunking can you please try to (temporarily - for test purposes only) configure interface vlan 2 at the 3500XL box and assign it ip address from the vlan 2 range (shutdown int vlan 1 first or use the "management" command) and then try to ping from the 3500XL switch to vlan 2 interface at the 3Com (or further vlan 2 workstation). I understand that you can configure CLI via the console port, otherwise PLEASE NOTE that changing the management vlan interface and ip address you LOSE THE CONNECTIVITY to the box.

Thanks & Regards,

Antonin

knichel67 · ‎10-18-2012

I shutdown vlan 1 and added vlan 2 with appropriate IP on 3500xl and added "interface vlan-interface2" on 3com with appropriate IP and was able to ping back and forth but still no go with DHCP on host connected to. I also added "ip default-gateway {ip to vlan 2 gateway}" and was able to ping from a computer in vlan 1 to my 3500xl and same is true from a computer in vlan 2.

I set a host connected to my 3500xl with an IP in vlan 2 and still cannot ping anything on schools network in vlan 1 or 2, but I can ping my vlan2 interface of my 3500xl (which this pc is connected to), and NOT the 3com at the other end of the trunk.

Looking closely at the 3com config, a port on the student network (vlan 2) looks like this...

port link-type hybrid

undo port hybrid vlan 1

port hybrid vlan 666 tagged

port hybrid vlan 2 untagged

port hybrid pvid vlan 2

I am not familiar with 3com, but that looks like vlan 2 is untagged? but with cisco, vlan 2 is tagged. Could this be a problem? or am I just not understanding what the tagged/untagged terminology means with 3com? Should I set vlan 2 to be native on the 3500xl trunk?

Thanks again for all of your assistance.

Mike

amikat · ‎10-18-2012

Hi,

Thanks for the information provided.

First of all let me answer your question and clear uncertainty about the vlan tagging:

At 3Com the port is configured as "hybrid" (Cisco used to provide support for the similar feature in 2900XL and 3500XL series - port type so-called "multi", it is not supported with new boxes anymore) - "short and dirty" saying: the port can belong to more vlans and you can specify the tagging - in your case, YES, the vlan 2 is untagged (and moreover it is configured as so called default vlan). But then within 3Com trunk to 3500XL the vlan 2 is tagged. The 802.1Q standard mandates that only 1 vlan can be untagged within trunk and this is so-called native vlan. Native vlan on both sides of a trunk should be the same and in your case it is vlan 1 (as you can see e.g. from the outputs you have provided). At Cisco the port is configured as "access" with the vlan 2 membership (only this one) and it is untagged on the output as well. So vlan 2 frames are transferred untagged at the input/output of access/hybrid ports but tagged within the "fa0/1-gi1/0/11" trunk. So far so good.

Now let us look to my questions and uncertainty as for your reply:

Are you saying that only now you have configured "interface vlan-interface 2" at 3com? If yes, then I do not understand how you can have reached vlan 2 from your 3500XL before. Are there any other routers (or L3 switches) connected anywhere in your network to vlan 1 (or vlan 2)? Can you please post the "display vlan 1 to 2" and "display ip routing-table" outputs at 3Com (I understand that you are using private address space - otherwise please modify/remove any sensitive information).

If I understand correctly you have been able to ping prom 3500XL vlan 2 inerface to 4800G vlan 2 interface via trunk. If so the trunk must carry vlan 2 correctly. Whast I feel confused from you reply is this:

I also added "ip default-gateway {ip to vlan 2 gateway}" and was able to ping from a computer in vlan 1 to my 3500xl and same is true from a computer in vlan 2.

Can you please be more specific as for the "{ip to vlan 2 gateway}" - was that interface vlan-interface 2 ip address at 3Com?

One more question: have you configured any ACL (relevant to our issue) atb 4800G box?

At the moment I am not making any suggestions as for DHCP issue as this can be due to the whole bunch of other reasons. My approach would be to sort the connectivity (including routing) first.

I hope my English makes sense.

Thanks & Regards,

Antonin

knichel67 · ‎10-18-2012

Wow, that is a ton of info. Thank You.

So, my understanding of tagging was correct. It seems the source of the problem may be tagging then. Since the 3500xl is tagging vlan 2 and the 4800g is not, then how does the packet get onto vlan 2 of the 4800g?

Are you saying that only now you have configured "interface vlan-interface 2" at 3com?

Yes, I only just added that to the 3com switch. We do have a router connected at the POP and it routes for all vlans. We do not have control over this router, our provider does.

display vlan 1 to 2

VLAN ID: 1

VLAN Type: static

Route Interface: configured

IP Address: 192.168.40.102

Subnet Mask: 255.255.254.0

Description: questar.org domain

Name: VLAN 0001

Tagged Ports: none

Untagged Ports:

GigabitEthernet1/0/11 GigabitEthernet1/0/13 GigabitEthernet1/0/25

GigabitEthernet1/0/48 GigabitEthernet1/0/49 GigabitEthernet1/0/50

GigabitEthernet1/0/51 GigabitEthernet1/0/52

Ten-GigabitEthernet1/1/1

Ten-GigabitEthernet1/1/2

VLAN ID: 2

VLAN Type: static

Route Interface: configured

IP Address: 192.168.140.109

Subnet Mask: 255.255.254.0

Description: questarstudent.org domain

Name: VLAN 0002

Tagged Ports:

GigabitEthernet1/0/11 GigabitEthernet1/0/48 GigabitEthernet1/0/49

GigabitEthernet1/0/50 GigabitEthernet1/0/51 GigabitEthernet1/0/52

Ten-GigabitEthernet1/1/1

Ten-GigabitEthernet1/1/2

Untagged Ports:

GigabitEthernet1/0/1 GigabitEthernet1/0/2 GigabitEthernet1/0/3

GigabitEthernet1/0/4 GigabitEthernet1/0/5 GigabitEthernet1/0/6

GigabitEthernet1/0/7 GigabitEthernet1/0/8 GigabitEthernet1/0/9

GigabitEthernet1/0/10 GigabitEthernet1/0/12 GigabitEthernet1/0/14

GigabitEthernet1/0/15 GigabitEthernet1/0/16 GigabitEthernet1/0/17

GigabitEthernet1/0/18 GigabitEthernet1/0/19 GigabitEthernet1/0/20

GigabitEthernet1/0/21 GigabitEthernet1/0/22 GigabitEthernet1/0/23

GigabitEthernet1/0/24 GigabitEthernet1/0/26 GigabitEthernet1/0/27

GigabitEthernet1/0/28 GigabitEthernet1/0/29 GigabitEthernet1/0/30

GigabitEthernet1/0/31 GigabitEthernet1/0/32 GigabitEthernet1/0/33

GigabitEthernet1/0/34 GigabitEthernet1/0/35 GigabitEthernet1/0/36

GigabitEthernet1/0/37 GigabitEthernet1/0/38 GigabitEthernet1/0/39

GigabitEthernet1/0/40 GigabitEthernet1/0/41 GigabitEthernet1/0/42

GigabitEthernet1/0/43 GigabitEthernet1/0/44 GigabitEthernet1/0/45

GigabitEthernet1/0/46 GigabitEthernet1/0/47

display ip routing table

Routing Tables: Public

Destinations : 7 Routes : 7

Destination/Mask Proto Pre Cost NextHop Interface

0.0.0.0/0 Static 20 0 192.168.40.1 Vlan1

127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0

127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0

192.168.40.0/23 Direct 0 0 192.168.40.102 Vlan1

192.168.40.102/32 Direct 0 0 127.0.0.1 InLoop0

192.168.140.0/23 Direct 0 0 192.168.140.109 Vlan2

192.168.140.109/32 Direct 0 0 127.0.0.1 InLoop0

I also added "ip default-gateway {ip to vlan 2 gateway}" and was able to ping from a computer in vlan 1 to my 3500xl and same is true from a computer in vlan 2.

One more question: have you configured any ACL (relevant to our issue) atb 4800G box?

What I meant by this was that on the 3500xl I added the command ip default-gateway 192.168.140.1 which is the default gateway for vlan 2 (the routers interface that connects to vlan 2 not the switch management interface IP). I have no ACL's configured at this time.

Just a thought, what if I were to make both ends of the trunk back to access ports? I don't need anything but access to vlan 2 on the 4800g.

--

Mike

amikat · ‎10-18-2012

Hi,

Thank you very much for the information provided. Based on that I have a bit more understanding of your network. Up until now I expected that your inter-vlan routing is done via 4800G switch but it is apparently provided by your Internet router. But we can return to this issue later should you be interested.

This surprise (to me) still does not explain while you cannot ping anything from PC in vlan 2 connected to 3500XL while you could ping your 3500XL address from the other end (and of course why DHCP does not work at your end for vlan 2). Can you please ask the 4800G administrator whether DHCP Snooping and also IP Source Guard or any ARP security functions are configured there.

BTW: do you have only one DHCP server serving for both vlans or one for each and (if it is not classified information) can you please let me know which platform it is implemented on.

Best regards,

Antonin

knichel67 · ‎10-19-2012

OK I have checked and we are not using any DHCP Snooping, IP Source Guard or Arp Security functions.

We have a separate DHCP server for each vlan and they are running on Windows Server 2008 R2.

Mike

amikat · ‎10-21-2012

Hi,

From the information you have provided so far I can see basic connectivity issue which I feel difficult to identify. If I understand you correctly then (after the Vlan 2 interface assignment at bothe ends):

- you could ping from 3500XL Vlan 2 interface to 4800G Vlan 2 inerface, which proved vlan 2 running correctly accross the trunk,

- you could ping from PC connected to 3500XL access port set to Vlan 2 to 3500XL Vlan 2 interface, which proved port status and Vlan 2 assignment OK,

- but at the same time you were not able to ping from PC connected to 3500XL access port set to Vlan 2 to 4800G Vlan 2 interface,

- and to your knowledge there is no configuration at 4800G to restrict packets/frames based on MAC, IP or DHCP assignment (you can configure next to nothing in this respect at 3500XL),

- I also understand that there is a direct link in between theese boxes (perhaps via a cable modem).

I can still try to help you to solve this issue but I am affraid I need to ask for the full configuration of both boxes for the case there is something rather special configured which I am missing. Should you decide to continue our co-operation will you please provide the following commands output:

3500XL - sh ver, sh vlan br, sh run,

4800G - display current-configuration.

Please feel free to edit/delete any sensitive information.

But before we go any further one more quick check: I recall that in the ancient times Cisco supported 2 different IOS trains for the 3500XL switches called Standard and Enterprise edition and that trunking was very limited/unsupported with the Standard edition IOS. You can find this information at the "sh ver" command output (last line). Provided you can see "...running Standard Edition ..." this may be clue to what you are experiencing.

Best regards,

Antonin

knichel67 · ‎10-22-2012

Thank you for your diligence. I will provide the configs on Tuesday. I was unable to retrieve them today.

--

Mike

knichel67 · ‎10-23-2012

Ok, here goes...

The configs are at the bottom...

From the 3500XL...

I can ping the vlan 1 and vlan 2 interface of the 4800g
I can ping a computer on vlan1 or vlan 2 off of the 4800g

From the 4800g...

I can ping the vlan 2 interface of the 3500XL
I CANNOT ping a PC connected to vlan 2 port on the 3500XL

From a PC connected to vlan 2 port of the 3500XL...

I can ping the vlan 2 interface of the 3500XL...
I CANNOT ping the the vlan 2 interface of the 4800g or beyond

Cisco 3500XL sh run

no service pad service timestamps debug uptime service timestamps log uptime service password-encryption ! hostname CGEC ! ip subnet-zero ! interface FastEthernet0/1 description Trunk to 3Com 4800g switchport trunk encapsulation dot1q switchport mode trunk ! interface FastEthernet0/2 - FastEthernet 0/24 description Standard Student Vlan ports switchport access vlan 2 ! interface VLAN1 ip address 192.168.40.108 255.255.254.0 no ip directed-broadcast no ip route-cache shutdown ! interface VLAN2 ip address 192.168.140.108 255.255.254.0 no ip directed-broadcast no ip route-cache ! ip default-gateway 192.168.140.1 snmp-server engineID local 0000000902000003E37F2A80 snmp-server community barf RO ! ! end

Cisco 3500XL sh ver & sh vlan brief

#sh ver Cisco Internetwork Operating System Software IOS (tm) C3500XL Software (C3500XL-C3H2S-M), Version 12.0(5.2)XU, MAINTENANCE IN TERIM SOFTWARE Copyright (c) 1986-2000 by cisco Systems, Inc. Compiled Mon 17-Jul-00 18:29 by ayounes Image text-base: 0x00003000, data-base: 0x00301F3C ROM: Bootstrap program is C3500XL boot loader CGEC-AIT uptime is 6 days, 28 minutes System returned to ROM by power-on System image file is "flash:c3500XL-c3h2s-mz-120.5.2-XU.bin" cisco WS-C3524-XL (PowerPC403) processor (revision 0x01) with 8192K/1024K bytes of memory. Processor board ID FAA0442W0AP, with hardware revision 0x00 Last reset from power-on Processor is running Enterprise Edition Software Cluster command switch capable Cluster member switch capable 24 FastEthernet/IEEE 802.3 interface(s) 2 Gigabit Ethernet/IEEE 802.3 interface(s) 32K bytes of flash-simulated non-volatile configuration memory. Base ethernet MAC Address: 00:03:E3:A6:57:80 Motherboard assembly number: 73-3904-11 Power supply part number: 34-0851-02 Motherboard serial number: FAB0440A1NQ Power supply serial number: PHI041201N1 Model revision number: A0 Model number: WS-C3524-XL-EN System serial number: FAA0442W0AP Configuration register is 0xF #sh vlan br VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/3, Gi0/1, Gi0/2 2 Qstud active Fa0/2, Fa0/4, Fa0/5, Fa0/6, Fa0/7, Fa0/8, Fa0/9, Fa0/10, Fa0/11, Fa0/12, Fa0/13, Fa0/14, Fa0/15, Fa0/16, Fa0/17, Fa0/18, Fa0/19, Fa0/20, Fa0/21, Fa0/22, Fa0/23, Fa0/24 1002 fddi-default active 1003 trcrf-default active 1004 fddinet-default active 1005 trbrf-default active

3Comm display current-configuration

version 5.20 Release 2202P15, Release 2202P15 # sysname 4800g 192.168.40.102 # undo voice vlan mac-address 0001-e300-0000 # voice vlan mac-address 0007-0e00-0000 mask ffff-ff00-0000 description 7941 # mac-vlan mac-address 0007-0e00-0000 mask ffff-ff00-0000 vlan 666 priority 0 # # irf mac-address persistent timer irf auto-update enable undo irf link-delay # domain default enable system # telnet server enable # undo ip ttl-expires # undo cluster enable # igmp-snooping # vlan 1 description questar.org domain igmp-snooping enable # vlan 2 description questarstudent.org domain # vlan 3 description video conf # vlan 666 description cisco phone # radius scheme system server-type extended primary authentication 127.0.0.1 1645 primary accounting 127.0.0.1 1646 user-name-format without-domain # domain system access-limit disable state active idle-cut disable self-service-url disable # user-group system # local-user admin authorization-attribute level 3 service-type telnet terminal local-user manager password simple manager authorization-attribute level 2 service-type telnet terminal local-user monitor password simple monitor authorization-attribute level 1 service-type telnet terminal # interface NULL0 # interface Vlan-interface1 ip address 192.168.40.102 255.255.254.0 # interface Vlan-interface2 ip address 192.168.140.109 255.255.254.0 # # **** Example of a Student Vlan interface interface GigabitEthernet1/0/1 port link-type hybrid undo port hybrid vlan 1 port hybrid vlan 666 tagged port hybrid vlan 2 untagged port hybrid pvid vlan 2 undo voice vlan mode auto voice vlan 666 enable mac-vlan enable broadcast-suppression pps 3000 undo jumboframe enable poe enable stp edged-port enable lldp compliance admin-status cdp txrx qos trust dscp # # ***** Trunk to my 3500XL # interface GigabitEthernet1/0/11 port link-type trunk port trunk permit vlan all undo voice vlan mode auto broadcast-suppression pps 3000 undo jumboframe enable lldp compliance admin-status cdp txrx # # **** Example of an Admin Vlan interface interface GigabitEthernet1/0/13 port link-type hybrid port hybrid vlan 666 tagged port hybrid vlan 1 untagged undo voice vlan mode auto voice vlan 666 enable mac-vlan enable broadcast-suppression pps 3000 undo jumboframe enable poe enable stp edged-port enable lldp compliance admin-status cdp txrx qos trust dscp # # **** Fiber connection to remote closet # interface GigabitEthernet1/0/50 port link-type trunk port trunk permit vlan all # # **** DaisyChain connection to other switch in closet interface Ten-GigabitEthernet1/1/1 port link-type trunk port trunk permit vlan all # ip route-static 0.0.0.0 0.0.0.0 192.168.40.1 preference 20 # # snmp-agent snmp-agent local-engineid 8000002B034001C6833EC1 snmp-agent community read public snmp-agent community write private snmp-agent sys-info contact helpdesk ###-#### snmp-agent sys-info location auto closet top snmp-agent sys-info version all # user-interface aux 0 8 authentication-mode scheme user-interface vty 0 4 authentication-mode scheme # return

Again, I cannot thank you enough for your efforts. This has been bugging us for over a year now.

--

Mike

amikat · ‎10-25-2012

Hi,

I went through all the information you had supplied so far but have not discovered anything which would point to the issue. I have also checked the release notes for the known caveats for both Cisco and 3Com/HP and have not found anything which could explain what you are experiencing. I have set up similar scenario in my lab but failed to reproduce the problem.

In my view what you can consider to try to further investigate the issue is this:

You can try to move (and reconfigure) the trunk to another 3500XL port for the case there is a trunking chipset problem. Similarly you can move the other end of the trunk to another 4800G for the case there is a H/W problem there.

You can try to upgrade the 3500XL IOS to the later release provided you have an access to one.

You can try to delete/rename "vlan.dat" file within your 3500XL flash and reload the box. The vlan database will be recreated.

You can check your vlan 2 ip addresses assigned manualy (switches and PC) for the duplicity (these should be excluded from the dhcp server pool).

To differentiate possible arp/broadcast problem from the connectivity issue tested via icmp you may configure static arp assignments at the vlan 2 PC and 4800G ends of the trunk (for the opposite endpoints) and try to ping again.

And of course finaly you may decide to monitor the traffic with the frame/packet monitoring tool (eg. wireshark) using the switches port mirroring/monitoring facilities to further try to discover where the problem could be.

I am sorry I cannot provide better assistance at the moment.

Best regards,

Antonin