I have a problem with high CPU load by DHCP Snooping process on Catalyst 6506 (WS-SUP720-3B, soft: s72033-ipservices_wan-mz.122-18.SXF11.bin). I have it enabled on 15 VLANS, in which there are subscriber devices residing, and sending DHCP requests through Cisco to DHCP server (Cisco acts as DHCP relay, and it's collecting the snooping database, I also use DAI).
Snooping database contains 6962 bindings now.
CPU load goes high only sometimes, and I don't have a clue, why it's going so high. It can load as high as 45-47% of CPU, like this:
When the load is high, the command: show ip dhcp snooping statistics is showing, that the overall quantity of
Packets Processed by DHCP Snooping is increasing rapidly. In normal situations, it's like 10-20 packets per second, but when the load is high, it's 1000-10000 pps.
But when I look at SPAN from my subscriber's VLANS, I don't really see any flood of DHCP requests, or something like that - everything looks as usual. Maybe, some of subscriber's devices are sending incorrect DHCP requests, that are causing packets to loop inside RP, or something like that? How can I detect that thing?
Also I thought, that if I enable the ip dhcp snooping trust mode on all of the Catalyst interfaces, the DHCP snooping will not process the subscribers DHCP packets, and I can, by exclusion of interfaces from one to one, detect, from which interface the problem is originating. But this seems to be incorrect, I turned the ip dhcsp snooping trust on all interfaces, and I still get spikes of CPU load by DHCP snooping process. Why it's still examining packets, even on trusted interfaces, is it ok?
And one more question - if I disable the ip dhcp snooping globally, will it clear all my existing bindings in snooping database?
I have a problem at a place where 5 ME3400 switches are connected in a straight line. I can't do much about the topology of that place, but the problem is they are all DHCP Snooping, but uni cast replies from the dhcp server further up the hierarchy gets eaten by the first switch! I can't really see why it not only inspects in and whines about it not being for itself - it then drops the message.
What have we done wrong (apart from the actual layout of that place, which I can't really change)?
Sep 28 13:49:29: DHCP_SNOOPING: received new DHCP packet from input interface (GigabitEthernet0/1) Sep 28 13:49:29: DHCP_SNOOPING: process new DHCP packet, message type: DHCPOFFER, input interface: Gi0/1, MAC da: 7444.012d.debd, MAC sa: 0013.1a4a.65c7, IP da: XX.YY.186.7, IP sa: XX.YY.186.1, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: XX.YY.186.7, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 7444.012d.debd Sep 28 13:49:29: DHCP_SNOOPING: binary dump of option 82, length: 20 data: [Code] ......
It really should just send it on, as with any uni cast not on the switch itself - it should go out Gi0/2 really. Why isn't it?
All the trunks are trusted, DAI is on (I've tried shutting it off, as well), port-security is used but it's actually not dying on the switch having the client computer, but the first one in the chain with dhcp snooping.
I have attempted to implement DHCP snooping and have been having some strange issues. I have 5 3560s taht I use for my edge and when I attempt to implement on all five, the VLAN that houses my voice data appears to no longer be able to recieve DHCP lease renewals so after the 24 expiration all of my phones lose their configs. Once I roll back the changes the voice VLAN comes back. The other VLANs seem to function correctly as theya re able to renew their DHCP addresses.
The 3560s tie into each other using GIG Ports 1 & 2 and the top and bottom switches tie into our core switch, a 4507. The config that I use is below, failry simple and straightforward.
4 of the 5 switches feed our general office vlans for voice and data however the 5th switch is there for expansion and not in use. As such I have left the config changes in place on it and have tied myself and a colleague into it and have been operating fine for over a week now. So the config that I use seems sound in theory and should work on the other 4 switches with no issue.
I am working in a environment that is classed as collapssed Layer 3 environment. We have a core 6500 with routed links to 3560's which are access switches.
We have layer 3 vlans on the access switches, one for data one for voice.On the layer 3 vlans we have ip helper addresses that are used for DHCP. The DHCP servers are located on the 6500.
I recently had a incident where someone plugged a netgear router into a desk point because they thought they could use it for a switch. This router then started to dish out IP addresses to people in the morning for those who came in and docked their laptops. 99% of people weren't affected because they have desktop PC's are their leases hadn't expired.
Now we have bpduguard, bpdufilter to prevent people from plugging in switches that send out BPDU's. However this doesn't prevent the above senario where someone plugs a router or a 'dumb' switch that doesn't send BPDU's.Because of the above senario I started looking at DHCP Snooping, but I am unsure on a couple of things.
With the topology of our network I understand that I don't need to configure IP DHCP Snooping Trust on the L3 uplinks to our core switch. From what I understand I just need to enable IP DHCP Snooping globaly and then on the VLAN's on the access switch (because of the L3 topology VLAN's are local to the access switches). Only if I had L2 uplinks to the core would I need to configure IP DHCP Snooping Trust on the trunk links.
I am trying to understand the basics of DHCP snooping. I have a just a 3560 switch and a laptop ( to get a DHCP address) and my DSL router which has a DHCP server running. On the switch I have enabled "IP DHCP Snooping" and "IP DHCP Snooping VLAN 1" plugged the laptop and DSL router in and the laptop gets and IP address, should it?
I thought all ports were untrusted by default so the DHCP server should be blocked at offering IP addresses? If I wanted the DHCP server to be allowed to offer IP's I thought I should need to trust the port.
I have a new catalyst 2960,and i want to enable DHCP SNOOPING,but,it doesn't work,the server is stilling offert addresses IP and it's not connected in a trusted port,the schema is very simple:1 switch catalyst 2960 PST-S,1 server dhcp and 1 pc client,the PC and the server are in VLAN 10,DHCP SNOOPING is enabled in all ports and no port is trusted,but the client get addresse IP after retyping ipconfig /release and ipconfig /renew in dos commande.the configuration and the version of the switch are in the file attached.I tested the same configuration in a catalyst C3560-24PS and DHCP SNOOPING work normally,i tested in other catalyst 2960-PST-S,but the same probléme:DHCP SNOOPING without effect,the commands typed is:
I got some problem with enabling dhcp snooping on 4500 (cat4500e-lanbasek9-mz.122-54.SG.bin) the topology is as below: dhcp snooping enabled only on CORE (with interface trusted to dhcp server)the problem is that I put these 2 commands
ip dhcp snooping ip dhcp snooping vlan 1
but it is not enabled on any vlan
SW-CORE#sh ip dhcp snooping Switch DHCP snooping is enabled DHCP snooping is configured on following VLANs: none DHCP snooping is operational on following VLANs:
[Code]...
On B1 if I turn it on there is a "1" in the section " DHCP snooping is configured on following VLANs:" but on core no.As you can see I did put the trusted on the interface in the direction to the dhcp.First I thought it can be a problem with option 82, I've read a lot about the issues with that, but the problem would be explicable if the client did receive IP address, but it does.
I am trying to find a command for dhcp snooping rate-limiting on a CatOS. The PFC card is PFC. PFC3B is said to support that command. But there seems no this command.
-6k> (enable) sh ver
WS-C6509-E Software, Version NmpSW: 8.4(5) Copyright (c) 1995-2005 by Cisco Systems NMP S/W compiled on Aug 3 2005, 13:26:46
I recently installed DHCP snooping on a 3750v2 switch (Version 12.2(55)SE4) and configured the uplink(Po2) as a trusted port. The problem is that clients cannot receive an IP address. When I disable DHCP snooping it is working properly. DHCP snooping is configured correctly but I don't have an idea how to resolve it. [code]I tested the solution on the same kind of hardware switch and firmware and it worked out fine. What is causing the clients not to receive an IP address from the DHCP server?
Just spoke to the TAC and didn't get the information needed. When configuring ip dhcp snooping database I am adding this to my configuration:ip dhcp snooping database scp://dhcpsec@192.168.1.50/home/dhcpsec/switch1.dhcp.database.txt..I assumed that to do this I would either specify the password on the command line, similar to the way its done when using ftp/http, or that I would need to create a public/private key.I have enabled scp and can manually copy a file from the switch to the linux server. So I believe I have all the aaa commands correct. Cisco WS-C3560G-24PS System image file is "flash:/c3560-ipservicesk9-mz.122-55.SE.bin".
i have a strange problem in my campus network.im trying to run port security on my access switches which they are 3550 with ios c3550-ipservicesk9-mz.122-52.SE when i run the port security with Sticky option, even i put 1000 mac address for just learning on the port but when i issue the switchport port-security command every pc connected to that port loses its connection with network UNTIL i enable dhcp snooping!!! all my client are getting they ip address from DHCP server but strange thing is that how on earth i have to enable DHCP snooping to port security work properly? also when i check the configuration under the interface when dhcp snooping is not yet enabled switch doesnt add any mac address under the interface so no one can work until i enable snooping and then switch adds mac addresses under the interface configuration.is this Bug on this version of IOS?[code]
we've an infrastructure were the Access is based on Cat3750G Stacks connected to both Cores using L3 connections.On the Access Switches are implemented the following features DHCP Snooping, IP Source Guard and Dynamic ARP Inspection and all is working fine since years...the DHCP Servers are on a dedicated stack which act as a SFarm.
On the Access Switches the port configuration is the following:the Uplink Ports to both of the Cores are configured in TRUST for DHCP Snooping and ARP Inspection the Access Ports, where the end-device are connected, are UNTRUST for DHCP and ARP Inspection with IP Source Guard Active Right now I've to add a new L2 switch on one of the Access Port and I'm wondering if this is possible since I've to keep on the Stack Access Ports all the security feature active and I've also to implement DHCP Snooping on the new L2 switch to avoid rouge DHCP Server...
I suppose that the uplink to the L2 switch on the Stack Access Switch should be left as it is connected to an end device...but the uplink port on the L2 switch should be set up as TRUST...isn'it? Keeping in mind that I want to implement DHCP Snooping also on this L2 switch to avoid that Rogue DHCP Servers will impact the end-device connected to this L2 switch...is this scenario possible??? or I can't do that and should leave DHCP Snooping only on the Access Stack.
I have a problem with DHCP. I have two 2960 connected with a port channel on ports 47 and 48 as trunk with native vlan 10. I only have this one vlan. In port 1 of sw 1, I have a C800 as DHCP server.
I have an AP autonomous with single ssid on vlan 10. When I connect the AP to sw1, I receive dhcp with no problems.When I connect the AP to sw 2, I’m not getting IP by DHCP.I have DHCP snooping working on vlan 10 on both devices.
The ports where I connect the AP are access ports on vlan 10 config as trusted.The trunk ports are also configured as trusted.The port 1 of ws 1 that goes to the C800 is also configured as trusted.
figure out why I’m not getting IP by DHCP when I connect the AP to the SW 2.The only I notice is that when I connect the AP to sw 2, I get on SW 1 the message of packet drop by option 82, but even after configuring ip dhcp snooping information option allow-untrusted on both switches, the problem persists.
I've configured ip dhcp snooping on several vlans I want to monitor and the binding table doesn't seem to be building.eature DHCP is on, global ip dhcp snooping is enabled, VLAN snooping is enabled on the vlan's I want to monitor and my trusted interfaces are also configured. Alas no binding entries in the table! 7K is running 4.2(6).
We have a DHCP SERVER implemented in a cisco router 2610.This router is connected to a switch cisco 2960 configured as DHCP SNOOPING. At the switch appear the next log message: [code] The ip address: 10.100.200.1 belongs to DHCP SERVER configured at router cisco 2610. What to do so these log messages does not appear any more? Do I need to do some configuration changes at some switch or router?
I need to apply DHCP snooping on 4500 series switches working as L2 in my Network. We have external DHCL Server in another location connected with 6500 series switch.
Running EIGRP Configured Voice & Data Vlan both DHCP Server -------- 6509 switch<----------------------------------->6509 Switch -------- 4500 switch ----------------------------------------------------------Ip Phones. (ving Redundant) (ving Redundant)
I need to know whether the configuration which I mentioned in scenario is enough for apply DHCP snooping in my network.
I have a pure L2 switching network and 2 hosts on the same vlan that want to communicate a protocol between each other using multicast packets.
I wanted to configure ip snooping only on this vlan and create a multicast group limited to only these 2 host ir order to make sure that the multicast traffic is only between both of them.
Since both are sender and receiver I´m not quite sure on how to configure this. In theory I also need to set an IP Multicast Address on the switch to where the hosts will send their multicast packets.
R1 is configured as host (no ip routing) with ip igmp join 239.10.10.10 on fa0/0 and R2 with ip pim sparse-mode on f0/0. SW1 is a Catalyst 3560 running IOS 12.2(25)SEE4 working at Layer 2 only in this topology (VLAN 1).
I configured SW1 for igmp snooping:
ip igmp snooping ip igmp snooping vlan 1
Basically, I can see 'snooped' muticast group (via IGMP reports sent by R1)
SW1#sh ip igmp snooping group Vlan Group Type Version Port List ---------------------------------------------------------------- 1 224.0.1.40 igmp v2 Fa0/2 1 239.10.10.10 igmp v2 Fa0/1, Fa0/2 SW1# SW1# SW1#
an attacker have configured his PC with an static IP address but there is no such entry configured statically in switch, neither in DHCP snooping database.now when he want to generate traffic will switch block him? because there is no entry of his PC in the switch database.
I have an issue with SRW2024P-K9-BR (SG300). Datasheet and configuration guide show me that is possible configure DHCP snooping in this switches, but web interface and console don't appear related menus/commands.
I'm using firmware version 1.1.2.0 and didn't found anything about this here.
I am configuring multicast in a environment where I have a 4506 at each site (4 total) and a 6506 as the core. Each 4506 is connected via layer 3 to the 6506. I have a mix of 3560s, 3548s, and 2960s connected to the 4506s and the 6506 via layer 2 trunk
I have multiple multicast sources and hosts communicating at a time (multiple cameras sending video / multiple computers receiving video). So this is not a scenario where there is 1 sender and many receivers. This would be many senders (~50) and some receivers (~10)
I configured ip multicast-routing on each of the 4506s and on the 6506. IGMP snooping is on by default on the 3560 and 2960 switches. CGMP is on by default on the 3548 switches.
I set up PIM sparse-dense mode and IGMP version 3 on each of the layer 3 interfaces for the 4506s and 6506 where they connect and on each VLAN that is sending or receiving multicast. Multicast is working throughout the network, however I am looking to verify the configuration as I scale this out to more clients on the network.
#1 - Is it correct to us sparse-dense mode in this configuration?
#2 - Do I need to configure a rendezvous points using AUTO-RP? (ip pim send-rp-announce INTERFACE scope TTL). Not sure here if I need to designate this and what to choose. Right now I do not have this and it is working, but documentation seems to infer that I need to designate this.
#3 - Is there any other configuration settings I should be considering? I hard to find real world configurations of multicast as examples or people that know multicast routing well.
I upgraded the IOS on 6506E, SUP 720-10GE, non-redundant, to a new one, rebooted OK. Switch seems to work fine but "show bootvar" shows the previous IOS name instead of the new one: s72033-advipservicesk9_wan-mz.122-33.SXJ3.bin.Removed the old IOS name on "boot var", gave it new IOS name, "show bootvar" now has correct new IOS name, write mem again and reloaded switch.It booted up OK but "show bootvar" still has the old IOS: "s72033-ipbasek9-mz.122-33.SXI2a.bin".According to IOS upgrade procedure, after all the upgrade IOS steps done, then just "write mem" then the "bootvar: will have the new IOS name, but on my switch it is always has the old IOS name ? How can I set the bootvar to new IOS name?
I have a Cat6506. There were 2 Sup 720 in it for redundancy. They told me they had problems with this thing in the past needing to go out and reboot the machine. I need to go out periodically because it goes into ROMMON. I type boot and it comes back up. One time though neither one would reboot. I had to take a third one out there and reconfigure it. Now it is starting to do the same thing. One thing I did notice is they never connected it to an UPS. It is plugged strait into the wall with power going to two outlets. I am beginning to think there are spikes in the power occurring and this is sending it into ROMMON.
Access-group only allows me to set the mode.access-group > mode > prefer > port > int g2/1,Those are the only options available to me, it doesn't allow me to go.ip access-group <name> in or out or access-group <name> in or out.
I realize the commands may be a little off, I don't have a switch nearby. When I get on our 3750 there are no issues, it allows you to apply the ACL the conventional way. I just can't seem to find any way to apply an ACL on an interface on the 6506 though.
I've got a pair of Nexus 7010's running vPC. I am having a Multicast issue with a cluster of Linux servers that need to talk Multicast for cluster/high-availability operation. All the servers need to talk to a single multicast address and I am having trouble getting them to communicate. I believe I need to enable IP IGMP Snooping Querier on the N7K's and it needs to be enabled on the VLAN where the servers reside. How to enable IP IGMP Snooping Querier on a VLAN ?
I tried to upgrade IOS from SXI2a to SXI9 in cat 6506 VSS. But the problem is that switch always boot with old IOS. I put the new IOS in sup-bootdisk and slave sup-bootdisk, bootvar is ok with new IOS: [code] Show bootvar is ok but switch always boot with old IOS SXI2a, some bug in IOS sxi2a???, I will try to delete de old IOS from sup bootdisk and try with the new one only.
I have PAT set up successfully on 6506 chassis - My outside address range is 78.24.112.114 255.255.255.240.Relevant parts of the config below: [code] This works fine but of course is only using the one IP address 78.24.112.114.how I can utilize the other outside addresses available or is this not really necessary? I've browsed through loads of Cisco docs.
We purchased two new 4948 with two 10GE uplink ports and upgraded the devices to run IOS 15. My 6506 is running Sup 720 with s77233-adventerprisek0_wan-mz.122-33.SXI9. Currently we have 4948's connected to the same 6506's with no problems. Today I tried to add the new switches with new IOS and it caused of of my 6506 core switches to failover. I can't explain why because it was close to start of business and couldn't do much troubleshooting. Currently we have four 4948 (running IOS 12.2(14) switches running Layer2 connecting dually to each of the two 6506 cores via 10GE fiber uplinks. I tried to add two more to the scenario, again running layer2 and dual-honing them to each of te 6506 switches. there are two 6506 core switches and they run HSRP and spanning tree is manually set to give priority to even vlans on one 6506 and odds on the other 6506. Also the new switches I tried to add did had rootguard applied as well as the uplinks.
We have to get this working and have no test environment to work with. We need to do this late this evening after close of business.
On another note, I have had problems upgrading some of my older 4948's to IOS 15. I followed Cisco's suggestion and upgraded the EPROM first and then the IOS upgrade took on three of the switches that were ordered rather recently. The four that were ordered in one batch will not take the upgrade even following Cisco's instruction and lots of other tricks. Nothing works. Having problems with IOS 15, in general?
