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 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 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 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 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 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 have setup a 4500 series core/router.. the customer decided to run dhcp off the router for whatever reason... I have 20 different scopes handing out to their vlans. Does each vlan interface need an helper address?
vlan 1 on router is 10.85.0.1 i used the ip dhcp-server command pointed to 10.85.0.1 and then for ex. int vlan 20 ip add 10.85.20.1 255.255.248.0 ip helper-address 10.85.0.1
i am now getting a loopback error on the router, and i believe this is the cause...
read the posts regarding vlans that are administratively down, they suggested that they are down if no ports are assigned to them, however I do have a switchport assigned, and the interface is still down. This is on the vtp server and on the clients. The vlan is not listed when issuing show vlan brief. Other vlans configured in a similar way do show and their interfaces are up. These are two Catalyst 4948-10G.Cisco IOS Software, Catalyst 4500 L3 Switch Software (cat4500-IPBASEK9-M), Version 12.2(53)SG5, RELEASE SOFTWARE (fc1).
I have an in production x2 4500's which I would like to add a new vlan and IP address to.
Sample config...
interface Vlan65 ip address 10.100.6.2 255.255.255.248 no ip redirects no ip unreachables no ip proxy-arp standby 65 ip 10.100.6.1 standby 65 timers 1 3 standby 65 preempt delay minimum 120
I've two Cisco 4500 running as core switches for huge and complex network. The two 4500 are going to act as dhcp server for several subnets. The easiest solution would be to split each DHCP pool in two, and assign the first half of the pool to one of the core switch and the second half of the pool to the second core switch. This would be a partial solution since if one of the two fails, the second core switch would not have enough dhcp leases available for all the devices connected for each subnet.For such a reason, I'm wondering if it the 4500 switches support a stateful redundant DHCP servers, so that the two switches can synchronize their DHCP lease tables. If this feature is available, I could define the same pools for both the switches without the risk of having duplicate ip addresses within the network.
Can you confirm that if I want to disable temporarily a dhcp pool on a 4500, I need just to shutdown the interface VLAN corresponding to a specific dhcp pool?
ip dhcp pool test network 10.X.27.0 255.255.255.0 default-router 10.15.27.250
We have observed WS-C4507R-E got rebooted while creating the L3 VLAN ( while No shut).Is there any known bug for below IOS ?cat4500-entservicesk9-mz.122-40.SG.bin,
On a 4500 switch port , defined as access vlan 10, if the user connects his own dhcp server ( instead of the normal pc that should be connected ), will it cause issues with my existing network. the existing network is all static ip. In above case, will the dhcp server start looking out and assign dhcp ip's , if a user unknowingly removes his static ip and changes to obtain ip via dhcp option on the lan properties.
On a 4500 switch port , defined as access vlan 10, if the user connects his own dhcp server ( instead of the normal pc that should be connected ), will it cause issues with my existing network. the existing network is all static ip. In above case, will the dhcp server start looking out and assign dhcp ip's , if a user unknowingly removes his static ip and changes to obtain ip via dhcp option on the lan properties.
1 x 4500 and 1 x 3560?They are gateways of 8 Vlans?They are doing HSRP in each of those Vlans?The 4500 is the Active?There is a DHCP Pool for each of those Vlans on both gateways using "ip dhcp excluded-address" I ensured that the range of provided ips by each DHCP server will not be overlapped Obs.: Reducing the lease time, I ended with the calls bringing related problems.
OK, every thing is blue, every thing is fine.But the network diagram is realy complex(41 switchs, 89 uplinks), and depending of how is the network flow, one or other server answer first or latter.
For many reasons I would like that the secondary DHCP server would answer only if the primary DHCP server goes down.To me, the bigger reason is that DHCP database would be only in one DHCP server.But there is other reasons.
I passed by many frustrated solutions:Try to force a delay on the answer on one of the servers. - Impossible.Try to disable DHCP server, and, using EEM, enable it only if router became active in HSRP. - I couldn't do It.
What I'm thinking now is use the HSRP resource to resolve it.On both routers I would put a "ip helper-address" pointing to an Virtual_HSRP_IP.And depending on which router is the active, him will answer the request.
My first doubt is:Would it work?The second doubt is:Could I use the same Virtual_HSRP_IP that exists on that Vlan(see example 1),or I would need to point it to a Virtual_HSRP_IP in a different Vlan(see example 2)?
Example 1 ----------------------------------- | 4500 | ----------------------------------- interface Vlan1 ip address 10.10.0.2 255.255.0.0 ip helper-address 10.10.0.1 standby 1 ip 10.10.0.1
I have a Cisco SG 300 28 port switch that I have set in Layer 3 mode. I set up a second VLAN on it (vlan 4). I also set up the scope for DHCP on a Windows server for both VLAN's. The problem I am having, is that VLAN 4 is not pulling DHCP at all. The DHCP server is connected to port 1 on the switch, and the specifics are as follows:
Stumped again with my Catalyst 2950. Everything is working perfectly with wan/dhcp/router on fa 0/1 with all ports assigned to vlan1. All devices plugged in connect to the router correctly with ip's being assigned via dhcp.Instead of hooking up by console port I want to be able to SSH or telnet in to the switch using any port while still maintaining the above functionallity. Is it possible to assign a dhcp assigned ip address to vlan 2 and have vlan1 and 2 bridged? Or is there a better way of doing this ?
1 Cisco switch stack (SGE2010) in L3 mode, 2 Vlans.
Vlan 1 = 192.168.0.253/24, untagged on all ports except 14/15 Vlan 2 = 192.168.22.1/24, untagged on port 14 and 15 SGE2010 default route 0.0.0.0/0 next hop 192.168.0.1 (Checkpoint UTM) DHCP Relay enabled DHCP server set to 192.168.0.16 DHCP interface set to Vlan2
[code]....
Expanding the ICMP entry, it appears that the destination is the pc client since it shows a Dell mac address, and the source is the Checkpoint UTM (Sofaware).
I can ping and tracert from the Checkpoint to my static IP on Vlan 2. The same goes for the DHCP server to/from Vlan2, so I am confused as to why the routing is failing. I have tried adding Port Fast to the stack ports, but nothing changes.
I am going to creat VLANs very 1st time therefore for test purpose I have following simple scnerio.I have created 2 VLANs , VLAN2 and VLAN3 on Cisco Catalyst 2960 series switch. Ports 1-12 is assigned to VLAN2 and Ports 13-24 are assiged to VLAN3. Now I have configured DHCP on Microsoft Server 2003 defining 2 scopes with following configurations.
Scope 1 for VLAN 2--- Range is 172.16.0.17 to 172.16.0.30 with subnet mask=255.255.255.240 . Server IP address 172.16.0.17 ( Note: Address 172.16.0.17 is excluded from dhcp server Scope 1 and give to the MS server itself) Scope 2 for VLAN 3----Range is 172.16.0.33 to 172.16.0.46 with subnet mask=255.255.255.240 .
Now in Cisco 2960 series switches, under Vlan 2 and Vlan 3, I have following configurations...
interface Vlan2 ip address 172.16.0.30 255.255.255.240 ip helper-address 172.16.0.17 interface Vlan3 ip address 172.16.0.46 255.255.255.240 ip helper-address 172.16.0.17
Now the problem is when i connect a client computer to any port from 1-12, It gets correct IP address from Scope 1 but when I connect a computer to any port from 13-24, it does not get the ip address.
Further I want to do inter VLAN comunication as well for that purpose i Have an ISR 2900 series router. What further configuration i will have to do on router for inter vlan communication.
Configured 6500 and 4500 to send netflow to a stealthwatch NADS.When visited by the stealthwatch engineer found that because i didnt have NDE configaured.i wasnt actually exporting any but the initial data in the flow.Now if i have got this right the command for this is - mls nde sender version 5
This is confirmed by looking at the following out put -show mls nde.Neither of these command work on my 4500 switch -does this mean that its not outputting all the data or do i not need to configure NDE or do i need another command ?
