Cisco WAN :: 3825 Routing Loop In OSPF Broadcast Network
Jun 23, 2011
I have 30 branch all over the country.There we have Cisco 3825 Series router at HO, and 892/k9m 1841 and 1811 routers in BO.My branches are being connected to HO via dual link which has been linked with two ISPs,both are Layer 2 link provided by the service provider,
-ISP1 subnet: 172.19.0.0/24
-ISP2 subnet: 172.20.0.0/24
usually i have the route pointing to HO ip from each branch routers. [code] Where, there are four branches acting as the gateway for the branch router 172.20.0.13. What cause the problem,and how can I solve this issue permanently?
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Sep 12, 2012
So the SG300's have STP on them and prevent network loops when other switches on the network also support STP too. However, if someone plugs in a non-managed switch that doesn't support STP with a network loop, is there anything within the SG300 switches to isolate and/or prevent that from happening?
(I currently have port mirroring turned on for one port and a network sniffer attached awaiting the incident to happen again).
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Jun 7, 2012
I have a bunch of 3750x switches that each have a 10 gig routed link back to a central 4507 (loopback = 172.30.255.255).We carved up a /24 (of course, the /24 doesn't really exist except in our address tracking spreadsheet) into a bunch of /30's for routed WAN links and /32's for loopback addresses.We started on the low end for /30 subnets (ie 172.30.255.0/30, 172.30.255.4/30, etc.).We started at the high end for the /32 loopbacks (ie 172.30.255.255/32, 172.30.255.254/32, etc.)
Well, when I try pinging 172.30.255.255 from the access layer 3750x switches, the 3750x seems to be treating it as a broadcast ping where it lists each member that responds instead of the regular !!!!! response (this makes think something is odd with the 3750x). Of course, only one member responds (the core). But even the core seems to respond with the other end of the /30 instead of the actual /32 loopback (which makes me think something is odd in the core). I could have sworn that I've setup similar topologies without problems (ie, using 10.0.0.0/32, 10.255.255.255/32, etc as loopbacks) and as long as the mask is a /32, it should work.Also, I can ping/ssh to that loopback if my laptop is on a directly connected subnet. But I can't do it from any of the 3750x switches (which are also directly connected).I've double checked for overlapping subnets, but nope. I don't see any. Routing looks fine. The actual /32 is being propagated everywhere properly.
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Sep 24, 2012
I have an AS-external route being redistributed into OSPF from a static route on one of my routers. I recently changed the static route from a /24 to a /26 and all of a sudden the link ID of the segment in the OSPF database went from the network address to the broadcast address: Code:
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Oct 4, 2012
I am using 1841 LAN router. Recently some broadcast is happening in our network when some users are connected. I need to block them automatically by detecting who are they.
I can block them manually but i want router to detect them and block.
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Oct 22, 2011
Recently we got a cisco catalyst 4500 and six 2960 access switches. I need assistance on configure spanning-tree and faster convergence on my network to avoid loop.
[code]....
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Jan 31, 2012
Our network feels slow and trying to find the best way to investigate this properly. We have Cisco chassis 4500 with mix of 3560/2950 Edge switches 1GB backbones and WLC/WCS in place. The network is broken into multiple V LANS and IOS on our switches haven't been updated in 3-4 years.
On a wireless laptop (G) with get throughput of 1-2MB/s transfer speed with usually 10 clients per AP and LAN we get anywhere between 7-15 MB/s transfer. Using wire shark on a wireless laptop we see a lot broadcast traffic from other clients and the same for LAN. What is the best way to troubleshoot performance issues on the network and where do I start?
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Aug 21, 2012
We have an OSPF network with four 6500 Distribution Switches. They are fully meshed and see each other as peers and are sharing routes. Off of one pair (Border) there is a setup of 3750G siwtches that go off to another network and they do not run OSPF. Between the Border Dist and the 3750G Switches we run HSRP. The 3750G side uses HSRP GP 192 and the Dist Side uses HSRP 192.There are static routes on the 3750G pointing to the Dist HSRP address to get back to network.Pings fail from the OSPF side to the HSRP address on the 3750G side.If I do a trace from the OSPF side to the HSRP address it hits one border dist switch then the other and fails.If I have static routes on both border dist switches pointing to the HSRP on the 3750side, do we need to change the metric on one dist so that it is preferred over the other or should the router Id take care of that?
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Sep 22, 2011
I have 2 ASBR routers, AGFR01RTR03 and AGFR02RTR03, performing OSPF to OSPF redistribution in both ways for the same ***. They also do summarization for our private addressing scheme. It is all working just fine for that part (neighbors, summarization, redistribution).
AGDC01RTR01 --- AGDC02RTR01 (OSPF 1000 ABRs)
| |
| |
AGFR01RTR03 --- AGFR02RTR03 (OSPF 1000 / 53 ASBRs)
Let's focus on AGDC01RTR01 with a specific entry here (IP subnet is fake) :
Routing entry for 1.1.1.0/25
Known via "ospf 1000", distance 110, metric 300, type inter area
Last update from 10.2.244.76 on GigabitEthernet5/1, 1d03h ago
Routing Descriptor Blocks:
* 10.2.244.76, from 10.2.1.249, 1d03h ago, via GigabitEthernet5/1
Route metric is 300, traffic share count is 1
[code]...
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Mar 14, 2011
Currently the OSPF network consist of 2 segment route via static route.One is AREA 0 and another AREA 10.Both network are seperate entity, only static route to route between 2 networks.But the static route do not provide the dynamically and flexibility, I plan to run routing between 2 networks via VLAN160 and VLAN162.
I still want to manitnace it was 2 different OSPFrouting domain.Can I run OSPF with differrent OSPF porcess ID?
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Apr 21, 2013
I don't do a lot of networking however during a cisco lesson the other day my lecturer briefly touched upon loop-back tests, would it be okay for somebody to very imply sum up exactly what loop-back tests do in a couple of lines and how they are carried out? (not in detail, so literally for example - a wire is put in from one end of the network to the other etc.) I don't really understand all the different wiring types etc.
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May 19, 2011
How can I identify loop or virus in the network? is there any command to find out these ?
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Jul 27, 2012
I have the task of replicating the router config on a 3825 router on a 3750 switch. Reason is we are taking out the router and replacing it with the switch to make use of the router for other functions.
Below is main part of the router config:
!
ip source-route
ip cef
!
!
multilink bundle-name authenticated
!
license udi pid CISCO3825 sn FCZxxxxxxx
!
vlan internal allocation policy ascending
[code].....
The 3750 switch I have runs C3750E-UNIVERSALK9-M, Version 12.2(55)SE3 on a LAN BASE license.
The first thing I have done is to order for a license upgrade to IP BASE which would give the support for OSPF routing.I do not see much of an issue with the Interface configs, however, I am not too sure about replicating the routing config on the switch.
My question is can I run the commands as shown for the OSPF routing on the switch? If not, can I get suggestions on how best to set this up on the switch?
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Apr 9, 2012
I have a 3825 router that I have setup with the following: [code]
Its on a trunked port to my 3750 switch. I am new to this compnay and havent changed it over to IP routing on the switch quite yet.Both Vlans are setup on the 3750 without an SVI. All hosts on VLAN 1 can ping both interfaces without issue.
If I put a host on the 172 VLAN it cannot ping anything on the router. If I put another host on the VLAN they can ping each other. If I put an SVI on switch the 172 VLAN hosts can ping the switch, but still not the router. ONce I put the SVI on the switch, it can no longer ping the router. I am giving the SVI ip 172.22.1.5/24.
I have verfied with TAC that the trunk is allowing the vlans to the router.
I have been working with TAC. They have asked me to update the code on the switch, but I think they are just punting. [code]
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Jun 6, 2013
I am trying to reproduce a Spanning-Tree loop in my lab that occurred on Ops, and for the life of me I cannot break it. The loop is very simple:
Cisco 2960------------FW that doesn't forward STP traffic-----------Cisco 2960
This created an STP loop. In my lab, I am substituting the FW for another Cisco 2960 with STP disabled and BPDUFilter on ingress/egress ports to stop the switch from sending BPDU's to the downstream switch to keep it in the dark, as the FW did on Ops.
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Nov 24, 2012
We have a couple of cisco SGE switches connected to a single DELL, between the cisco switches we have a trunk interface. I'm not sure which setting should be configured on the switches to get it working because a loop is occuring.
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Feb 17, 2013
I have a Catalyst 3560-X PoE that suddenly stopped working. I plugged in via console and below is the output I received. It scrolls constantly and I am unable to enter ROMMON mode or stop it from scrolling. I've read of a possible problem with the IOS version but I'm unable to verify due to not being able to stop the scrolling.
Switch uptime is 4 minutes, 4 seconds
cisco WS-C3560X-24P (PowerPC405) processor (revision A0) with 262144K bytes of memory.
Processor board ID FDO1522R2AY
[Code].....
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Apr 14, 2007
We recently wanted to swap our existing WS-SUP720-base with a WS-SUP720-3B in a 6513 chassis.Had the existing configuration config saved in a txt file and replaced the supervisor. Booting went fine and we pasted in the original config. There was one failure message about unnsupported command but didnt take further notice."boot system flash sup-bootflash:" was probaly the line that the 720-3B didnt support.After wr mem and reload it went in continious loop and rebooting due to inncorrect boot device. Had to put back the old supervisor and have now the 720-3B in a 6504 chassis. Tried some commands in rommon, but are not getting any further.
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Dec 31, 2012
I've came across a very odd topology to deal with where everything is connected to everything, without proper utilization of VLANs.
- I've an L3 SW and a 3745 RTR at core
- Both are carrying same subnet to an L2 distribution switch that connects server farm within the same subnet (i.e. 1.1.3.x subnet)
- The L2 switch works as a passive switch, hence another network say, 1.1.2.x has been plugged into it as well.
- This L2 switch extends to other switches without configuration of any VLANs or STP and distributes 1.1.3.x network.
Periodically and unexpectedly, the router starts hanging and utilization goes beyond 80%, and there's nothing at all that is observed in "sh proc cpu" to be eating router resources. Its quite difficult to observe the pattern, as its random.
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Jun 7, 2013
when this error occurs
we can't see the cdp neighbor and the wireless crash.
we login onto the ap with console , we can see the error log : “Network interrupt loop detected” . last forever
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Aug 27, 2012
We have 2 sites, each with 2 x 4506 switches which will be connected togther using an etherchannel. The switches will provide access ports for client devices and will be configured with HSRP to provide gateway redundancy. SW1 will be HSRP active.2 metro ethernet links will be installed in each site which will connect back to our HQ sites. OSPF will be used over the backbone to provide resiliency and to allow shortest path routing to each HQ and to prevent traffic over the HQ to HQ link.
The 4506 will be trunked togther with an SVI for providing OSFP adjacency.For the traffic flow from SW2 to HQ2, traffic will hit SW1 and then route back to SW2 and then to HQ2. Is this the best way to do this? Should a second link be connected between switches just for routing or should something like GLBP be used?
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May 22, 2013
I am attempting to filter a specific host(s) from my OSPF routiing table on a ASA 5550 (ABR) using LSA prefix lists. However, when I look at the other routers in that area, I notice that ALL LSA type-3's are being removed (10 hosts are now missing from the routing table). I have verified the filter is working on the ABR, but I can't figure why ALL hosts/routes that were coming into the area are now being filtered instead of the specific one that I want to filter out.
Here is the config on the ABR:
prefix-list pdm_pl_000 seq 10 permit 206.253.180.137/32
!
!
router ospf 1
network 10.0.0.0 255.255.255.0 area 0
network 10.150.10.0 255.255.255.0 area 10
network 10.150.252.0 255.255.255.224 area 10
[code]....
The 206.253.180.137 host is actually coming from Area '3'. Am I doing something that is removing all type-3 LSA's?
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Mar 1, 2012
I Like To Intentionally Create A Layer 2 Loop in My LabI have 2960 and 3750 switches and servers with multiple NIC's and also Some PC's and Hubs. Connections and Commands And Features Which Sould Be Disabled or Enabled)
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Oct 25, 2011
I am having an issue with this device after setting the ip address and rebooting. I have tried renaming the config.text file without success. I have also tried the steps mentioned here: [URL]
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Feb 19, 2012
we recently had on our network a simple layer 2 loop problem, with big effects.Here is the situation: we have a C3750 switch, with STP activate on all ports.We don't have total control on this switchs, and for some reasons, it is possible that people connect a 2d switch on it (Cisco or non-Cisco).What happened several times is a classic case: a person interconnect 2 ports of this 2d switch, creating a loop. As the loop is created on the 2d switch only, the 1st switch detect no loop, the the uplink port keeps up.Afer this loop created, a broadcast storm occurs through the link between 1st & 2d switch .. and the storm propgates all over the LAN.I try to find some solutions to avoid that. One thing I would like to do is to find a mecanism on the first switch, which can permit to block the uplink port on the 1st switch if it sees the same MAC address as source in the 2 directions.Note that storm control, even configured to a quite low value (ie: 2Mbps) is not efficient enough to protect equipment (we have had big CPU impact on LAN equipments).
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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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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 17, 2012
Do Cisco Catalyst (IOS) and specially Cisco SG300/500 support a similar feature to HP's Loop Protection or DLINK's Loopback Detection? This is an interesting feature to avoid loops caused by unmanaged switches.
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Mar 25, 2012
I have an environment where i have two nexus 7010 switches, along with 2 nexus 5510's. I need to run OSPF as a layer 3 routing protocol between the vpc peer links. I have 1 link being used as a keep alive link, and 3 other links being used as a VpC link.
1) Is it best to configure a separate Vpc VLAN i.e 1010
2) Is it best to configure a vrf context keep-alive
3) just have the management address as the peer ip's.
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Jul 26, 2011
I have three eigrp configured routers A, B , C in a single broad cast LAN.I want to deny router A eigrp peering with router B, need to retain A peering with C. A router:no neighbor <B router lan ip> under router eigrp will work ?or how can i deny using the multicase ip address 224.0.0.10 usinng access lis an din which direction i need to apply.
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Jul 17, 2012
I have a cisco 3825 router with two GE interfaces. GE0/0 is connected to a switch through ethernet cable. I have configured the GE0/0 interface with IP address. I have also configured static route for the local network. However, now I can only ping the GE0/0's own IP from the router. Here are the running-config:
hostname Router
!
boot-start-marker
boot-end-marker
!
!card type command needed for slot 2
enable secret 5 $1$4gxa$sykc0mcaxpCIrGc86i1ZE.
[code]...
The 10.1.52.1 is the current gateway on the 10.1.52.x LAN.
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Jan 19, 2012
I have a 3925 Router with a 48 port switch module (part number SM-D-ES3G-48-P). I have no problem accessing the 3925 Router, but when I go into the 48 port, I get an error that reads
Error Hardware not supported by firmware. Try loading a newer software instead. System Resetting...
I know that the wrong IOS is installed on the switch, but the problem is that this is an endless loop. The switch resets then comes back to the same error. How to get the switch out of this loop so that I can load the correct IOS.
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Aug 18, 2012
The following error was seen on the switch and the Diagnostic Test Loop back failed following a new WS-6748-SFP module installation.Fabric in slot 5 detected excessive flow-control on channel 3 (Module 4, fabric connection 1)
Tried Hard reset of the module and still the error persist.
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