Cisco Switching/Routing :: 3550 - Two MST Instances Enabling Root Guard
Jan 12, 2012
I have 2 3550 12G switches that I use as core fiber switches. Switch 1 is the primary for 1/2 the V LANs and Switch 2 is the primary for the others using MST with 2 instances (I am not including the default 0 instance). I am using HSRP to provide redundancy. So far so good.
Recently a tenant in my building would like to use their own switch for data but still needs access to a V LAN on mine for voice. Again not a problem as I can configure a trunk port and give them what they need. My concern is that if they try to configure STP on their switch can they take down mine. Are there some preventions that I can put into place, such as root guard, that work with MST? What happens if they too set up MST can they kill mine?
Switch 1 is the root for 1/2 the v lans and Switch 2 is the backup root. The scenario is flipped for the other 1/2.
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Dec 15, 2012
in my LAN the all access layer switchs/stacks are connected directly to core backbone switch (cisco 6509) via sfp fiber-optic, i want to protect my spanning tree setup with the "root guard" command.
1. where would i set this ? on uplink ports on access layer switches ? or on core backbone ports to which the access layer swithes connect to?.
2. can this be set on active (production) ports without downtime?
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Mar 24, 2003
Currently it seems as our 3550's doesn't send traps when bpdu-guard sets a port in err-disable state. Or DFM doesnt recognize it.Is there a way to get a DFM alert when a 3550-port gets into err-disable state?
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Apr 24, 2013
I read that maximum spanning tree instance number is 128, is there any switches that can go more than128 instances ? or can we do this from IOS updates ?
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May 22, 2013
We have an environment where users create a lot of bridge loops. We have tried to send E-mails about it and educate the users but it is almost a lost cause at this point. The loops are created when users don’t pay attention and they plug a patch cable coming off of an access port up to ANOTHER access port by mistake.
All of our access ports are from 3750 stacked switches. The way we tried to deal with this in the beginning was with BPDUGuard and ERRDiable (BPDUGuard) auto recovery. We turned BPDUGuard on globally and left BPDUGuard auto recovery at the default value (I believe it was 30 seconds). so a loop would be detected and after 30 seconds, the switch would try to enable the port and if the loop still existed, close the port for 30 more seconds. Then we started having problems with printers getting "fried". Their NICs would die out and the control board would need to be replaced. After a lot of troubleshooting and testing, it was determined that allowing the ports to come out of ERRDisabled state would flood the network and the packets would generate in the millions per second range and fry the NIC of these printer.
The fix for this and saving the printers was terrible. We removed ERRDisable auto recovery and just let the ports that are looped stay in an ERRRDisabled state. We wait for the user to figure out the loop and try to use the port and then put in a work order. Then we physically visit the site and verify the port was shut (ERRDisabled) from a loop and we bounce the port (shut/no shut) and everything is resolved. I did lab tests with a switch looped and a printer on the switch and watched it fry. We have had no printers fry after we removed the auto recovery protocol at every location. Only the locations where loops existed and auto recovery protocol running were printers going bad. What I found during my lab tests was that each time the port was auto-recovered (yes, for that millisecond while it checks if a loop still exists), more packets were re-generated and eventually enough was re-broadcastthat printers would go down. We never had a problem with computer NICs. I guess the cheaper printer NICs couldn’t handle the broadcast storms created by this. I tried playing with the auto recovery timers and even the highest setting would eventually re-create these storms.
So my question is what best practices are others using? Should we get rid of BPDUGuard and just try to let spanning-tree handle these bridge loops? Is there something else I can try? I’m not CCNA by any means, just trying to do what I can in my environment. Manually visiting sites when loops occur is becoming more and more my job, though and I have plenty of other things to be doing.
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Mar 24, 2013
I have a strange issue where spanning-tree is blocking vlans through a mesh network.Here is my set up.
2-Cisco 3560's that have two trunk ports set with do1q and a native vlan of 2. I'm allowing a client vlan (2) and a voice vlan (103) to come over the trunk. They have a native vlan of 2 so the mesh APs can get an address through DHCP. Spanning-tree loop guard is also enabled.
When connected to the mesh network, the voice vlan is being blocked by spanning-tree. I get the following erros:
000129: *Feb 28 19:24:58.289 EST: %SPANTREE-2-LOOPGUARD_BLOCK: Loop guard blocking port FastEthernet0/1 on VLAN0103.000130: *Feb 28 19:24:58.448 EST: %SPANTREE-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port FastEthernet0/1 on VLAN0103.
Eventually the loop is cleared and the port is set back to a forwarding state from a blocking state. I don't want to disabled spanning-tree loopguard since I don't want to create a loop. The mesh network is supposed to act as a P2P connection between two switches. As a test I disconnected the APs from their trunk ports. I then used a cross over cable to connect the switches and no spanning tree loops occured. The mesh doesn't have STP enabled on it and should just be acting as an over-the-air connection from one switch to another.
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Sep 9, 2010
I'm having some weird issues with our 3560 that's connected to an MPLS line. The speed of the port plugged into the providers equipment is 100Mb, but we're only allocated 10Mb of bandwidth from them, I tried to police our traffic out of the port using srr-queue bandwidth limit 10, however when I do that I get some really weird bandwidth results.
Using iperf I've run bandwidth tests with srr-queue bandwidth limit enabled and with it disabled, when it's disabled I get the full 10Mb as expected, however once I enable it I'm lucky to get 5Mb, and while the test is running connectivity between sites is almost useless (which is not the case if I disabled bandwidth limit). Is there anything special I should be doing when I have this enabled? I also have priority-queue out enabled with only one dscp marking placed in queue 1, with very little traffic hitting that queue, but regardless of what I do I can't get the expected bandwidth with the bandwidth limit command, even if I place my iperf traffic in that priority queue.
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Nov 16, 2011
My clients switch is running out of Spanning-Tree instances (c3560 only supports 128 instances). I know that running RSTP with VSTP can mitigate this that all instances over 128 will be handeled by RSTP, but before I implement this are there any other thoughts out there on how to mitigate this. Would MSTP be able to handle more STP instances or MISTP perhaps?
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Sep 29, 2012
I've just set up DHCP Snooping and IP Source Guard on our SG500 series switches. It seems to work quite well, except when a wireless host roams from one AP to another (on a different switch port), all traffic from that host gets blocked.
I can understand why this is occuring, but I don't know what I can do to work around this problem.had success with roaming WiFi machines in conjunction with IP Source Guard?
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Oct 16, 2012
I have a setup where - I have a cisco stack (4X SGE2010 Switches) trunking over to a 3COM switch. Both switches believe to be the "ROOT" of the network. Note The 3COM is running RSTP as opposed to the Cisco Stack which is running normal STP. To my understanding of STP - Essentially STP is not functioning! Both switches believe to be the "ROOT" so they don't shut ports down. (We are currently having major issues with ports going up and down for seconds at a time on both switches)
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Feb 16, 2013
I config vlans 21-23 on 3750 A and B switches.I config B switch to be Root Bridge for all vlansspanning-tree vlan 1,21-23, priority 4096 sh span tree on B switch 3750B# sh spanning-tree.
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Feb 11, 2013
I have two 6509s both with single FWSMs running in transparent mode with bridged Inside and Outside VLANs.I have my Core A set to STP priority of 8192 and Core B set to 16,384 to make Core A the root for all VLANs.Problem I have is when I look at spanning-tree on Core A for Inside VLAN 324 it states to get to the Root go via PO100 (Cost of 9) and that the Root also has a Priority of 8192, but as the designated Root has a lower MAC address it's pointing to the etherchannel. PO100 is L2 Etherchannel between the Cores.Moving accross PO100 to Core B and running the show spanning-tree command I can see that to get to the Root Bridge I need to go via PO272. PO272 is the internal Etherchannel to get to the FWSM on the Core B Switch. This shows a cost of 6 to get to the Root and a mac address of the Root Bridge which resides on Core A (Outside VLAN 124)To give some perspectibe,theoutside VLAN of the pair has it's STP ROOT on the Core A switch as intended?
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Jan 18, 2012
I have an Extremely Old switch that I need to connect to my network. Because it is so old I don't want it to become the Root Switch.
what is the command to change the priority. (Honestly I don't remember if it has to be a lower number 1 or a higher number ). Always get that mixed up. I've read about root guard, but I would like to prevent it manually. (It is a small network after all)It is a Cisco 2950.
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Apr 1, 2013
I have two locations DC and Corp connected to each other via Point to Point Circuit. I have forced the two core switches setup as GLBP pair to be primary and secondary for certain VLAN's including VLAN1.I have a switch in our Corporate office 3750 which is where the point to point circuit terminates. VLAN1 SVI is manually shut on that switch. Also the priority on VLAN1 is increased manually like this, "spanning-tree vlan 1 priority 28672".
Now the issue is that the Primarey Root Bridge in the DC is the root bridge for VLAN 1. But this other switch 3750 in our corporate office also is a root bridge for VLAN1. [code]
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Nov 13, 2012
I have a cisco 3560 8 port switch. I really would lime to have the webinterface enabled. So i downloaded the archive from cisco. I extracted the archive to the flash of the switch. After rebooting the device everythings looks fine, but the html folder is a subfolder. It looks something like this: flash:c3560.../htmlI my understanding to enable the webinterface the html folder should be here flash:htmlHow do i move the html folder from the subfolder to the root?
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May 3, 2013
We have a problem with a Cisco 1400 Bridge. This equipment can not bridge to the other root or not root mode. I can see a message "Interface Dot11Radio0 Radio transmit power out of range" and the MAC Address of Dot11Radio0 appears with 0000.0000.0000.I set the local power to 18 but the MAC Address is still in 0000.0000.0000.
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Oct 18, 2011
i got the problem with 1300 bridges,root bridge with omni antenna and non root with sector antenna , it can associate and can pin each other , but whenever i try to browse several web pages its get timed out and radio was down.
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Jul 18, 2011
Any working configuration between two BR1310's in Root/Non-root mode? The documentation is vary vague and i can't find anything more secure than WEP. Is it possible to use WPA with radius authentication?
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Oct 25, 2011
I have an 881 router here in house and am attempting to enable the gui interface on the router.
I have tried the steps to enable http but have not had any success. Below is the IOS Version and the portion of the show config that reflects the http allow:
ROM: System Bootstrap, Version 12.4(15r)XZ2, RELEASE SOFTWARE (fc1)
Cisco 881 (MPC8300) processor (revision 0x100) with 249856K/12288K bytes of memory.
Processor board ID FTX1249Y16Q
[Code].....
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Nov 19, 2012
after installation of demo versions of 2900-SEC-TEMP & 2911-2921-SSLVPN-TEMP & rebooting the 2911 router I do not have access SSL commands.Show license indicates that 2900-SEC-TEMP & 2911-2921-SSL-TEMP licenses are active but NOT IN USE.
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Jan 28, 2013
does enabling jumbo frames on the 6509 require a reboot?
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Apr 26, 2012
I have two WS-C2960-24TC-L Switch with Software Ver 12.2(25r)SEE6 with image c2960-lanbase-mz.122-35.SE5.bin and 12.2(25r)SEE1 with image c2960-lanbase-mz.122-25.SEE2.bin currently on it.
I want to enable SSH connections on the switches and believe I need to import the cryto image onto the switch. I would like to upgrade it to new version that can also support ssh connection but not sure which image to download from cisco. The switches are now live.
System image file is "flash:c2960-lanbase-mz.122-35.SE5/c2960-lanbase-mz.122-35.SE5.bin"
cisco WS-C2960-24TC-L (PowerPC405) processor (revision H0) with 61440K/4088K
[Code].....
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Nov 12, 2012
I met a strange problem after enabling flow-control in 2960s.my enviroment,
- 2 cisco 2960s 24ts-l have been created a stack
- IOS is 12.2(58)se2
- all ports have been enabled flowcontrol receive dersied
via show flowcontrol, I can see each Gigabyte Port have been enabled "flowcontrol receive desired" but, when I do the following tests
- connect equallogic ps4000xv to the port 21, I found the status of port is "input flow-control is off"
- connect one server with Broadcom Gigabyte Network adapter, which has been enable TX ON RX ON, or Auto, the status of the port is still "input flow-control is off"
I guess, the port status should be ""input flow-control is on". Test them with another port, I got the same result. why?
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Oct 4, 2012
I have a pair of N7K's in vPC topology with some FEXs attached. I am looking into enabling Jumbo frame on the N7K as well as the FEX. I understand Jumbo frame is enabled globally by default.
My question is I have some interfaces in a port-channel that I need jumbo frame enabled. Do I enable it at the port-channel interface or at the physical interface ? and is the change disruptive to the network ? I am running NX-OS 6.0.2.
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Feb 16, 2012
I have installed a EHWIC-4ESG card into my 2911 router running IOS Ver 15.1(4)M2. When I do a show diag, I can see the card, but I get the following line "Could not get card instance pa_bay=0 slot=0." Am I missing a step, do I have change something, is it not compatible (all that I have read, states that is)
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Feb 20, 2013
One one of our Cisco 6509s I've globally enabled QoS and set a port to "trust cos". However when I look at the queueing for that interface, I notice that the receive queue thresholds have not changed to the default.
I'm kind of new to QoS so I'm not sure if I'm missing something.
We are using a Cisco 6509 running 12.2(33)SXI3 using the WS-X6724-SFP card. I thought I'd be seeing the default tail-drop thresholds, but instead I still see the defaults as if QoS were not enabled:
Queueing Mode In Rx direction: mode-cos
Receive queues [type = 1q8t]:
Queue Id Scheduling Num of thresholds
[Code].....
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Apr 18, 2012
I have a collapsed core design with routed ports between all components. Access layer switches, data center switches, core/aggregation. All routed (no spanning-tree at all).Now...I have to add an IBM BladeCenter with a BNT layer 3 switch to my topology. However, those nasties don't seem to support routed ports.How can I have a routed port on my cisco switch and a standard access port on the BNT and still establish an adjacency with an SVI? I am running OSPF, but I am labbing this in my home lab with 2 x 3550s and EIGRP.
On SW2:
*Mar 1 00:57:00.711: EIGRP: Received HELLO on Vlan100 nbr 10.1.1.1
*Mar 1 00:57:00.711: AS 999, Flags 0x0, Seq 0/0 interfaceQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
*Mar 1 00:57:02.303: EIGRP: Sending UPDATE on Vlan100 nbr 10.1.1.1, retry 9, RTO 5000 tid 0
*Mar 1 00:57:02.303: AS 999, Flags 0x1, Seq 17/0 interfaceQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
[code].....
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Jul 24, 2007
Does Catalyst 3550 switch support inter vlan routing ?
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Apr 11, 2012
Is L3 ip routing on by default in 3550s? If so is the "ip routing" command visible in the config file? If no - I assume that one would enable L3 routing with that config command.In general terms are there any IOS devices where ip routing is enabled and one would not see the "ip routing" command in config. I.E. if that command is not visible in the config could you assume there is no L3 capablity in that device?
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Sep 18, 2012
The layer 2 switches are connected to layer 3 Switch via trunks, and routing between layer 2 switch ports with configured SVI's on 3550. All working fine. Now I'm trying to configure routing between 2800 and 3550, I tried connecting both Straight Throught and Crossover cables to the 2800 Fa0/0 and Fa0/1 ports as well as the switchports on 3550
No switchport commands are configured however, the lights do not go on for both straight through or crossover cables. I tried connecting 1750 routers but same result. My goal is to have all the VLANS routed to the internet with configuring NAT translation the router.
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Apr 26, 2012
I have a 3550 l3 switch configured as follows:
vlan 10 ports 1-10
vlan 21 ports 11-20
vlan 30 port 21-30
vlan 40 ports 31-40
default vlan should be vlan 21
I have the servers, switch and router connected to vlan 21. Vlan 21 works great I can browse the internet, but I cannot ping any other vlans. router is connected to fa0/19
[code]
Building configuration...
Current configuration : 4833 bytes
!
version 12.2
no service pad
[code]....
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Mar 10, 2013
I'm having some problems setting up vlans to talk to each other on a 3550-12T switch. Its quite a simple setup I have, but I need to split my network up.
Currently I have a network of 192.168.25.0 255.255.255.0 I want to create a new vlan network of 192.168.30.0 255.255.255.0 So I have configured my vlan1 (default vlan) to have an ip of 192.168.25.250 for getting to the management page
I have created a vlan2 of 192.168.30.1 255.255.255.0 ?I have a port 10 linked to one of my 3560G's?In port 9 which is on vlan2 I have my pc plugged in with a static ip of 192.168.30.50 from the router I can ping any device on 192.168.25.x.
I can not ping 192.168.30.1 (which is my vlan2) nor can i ping the PC.
I have enabled ip routing But I dont have a default route, this is becase we don't have a router on the network.
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Dec 2, 2011
I've been working with these two Cisco devices in my home off and on for several months now but I just can't take it anymore, I'm about to throw them away and go back to Linksys router.
I have a Cisco 2600 Router with only one Ethernet card in it so I have to trunk from my 3550 Switch to that device. I'd like to have my ISP and all users plug into switch and all trunk back to the router's sub interfaces. Currently, I have started over...again, and am unable to simply get the router and switch to ping each other if I put sub-interfaces on the router. See my configs:
2600 ROUTER:
Router#sho run
Building configuration...
Current configuration : 555 bytes
[code]......
3550 SWITCH:
Switch#sho run
Building configuration...
Current configuration : 2302 bytes
!
version 12.2
[code]..........
Port F0/24 is in VLAN 1, as are all ports but Port F0/1 which is my desktop PC. I mocked it up in Packet Tracer and it works just fine. This is just a simple setup and I'm making sure I can ping between switch and router before I move to each next step.
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