Cisco Switching/Routing :: 3560 G - Static DHCP Client Drops Connection
May 31, 2012
i am not sure if this is something with my DHCP setup or not, but it certainly seems to be the culprit. I am running a 3560G and using it as DHCP and to do V LAN routing (Geiger protocol). I have 10 pools configured with a few static addresses per pool. Now to get down to the problem. I have a computer (and this problem seems to be a gremlin as it changes what computer is affected quite often) that will connect, get its IP, immediately disconnect, then send out a DHCP req again. The computer has a static assignment in the pool, and for the brief second that it connects, it gets the right address. If i move the computer to another v lan, all works right. If i delete the static entry it will get an address in the right v lan no problem. The command i have been using to add static entries is:
address xxx.xxx.xxx.xxx client-id 01xx.xxxx.xxxx.xx
That seems to have been working on all my static routes except for a bank of computers in vlan3. I have went as far as to delete the pool and recreate it, heck i even recreated the v lan and i am still having issues. Below are some snippets of the running config for review.
The DHCP Pool for the affected LAN:
ip dhcp pool Dev3
network 192.168.3.0 255.255.255.0
boot file bootx86wdsnbp.com
next-server 192.168.1.78
dns- server 192.168.1.8 192.168.1.78
[Code] .....
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Jul 30, 2012
How to configure cisco 3560 to force the client only can get ip by dhcp-relay server ?
The company i am working in has 5 vlans which have been set an lay-3 switch(3560), uses the dhcp-relay server .(in svi configuration: ip helper-address X.X.X.X) well , that works ok~
Now , I got my problem: I need to force the client only can get ip by dhcp-relay server, that means if anyone set static IP manunally , he can't really access to anywhere (to provent anyone set static IP with malignancy )
I know if a h3c router , how to set this configuration n svi configuration : dhcp relay security address-check enable )
the how to configure on a cisco 3560 ?
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Feb 10, 2012
I feel that 3560 and 3750 perform differently with the following two commands:
srr-queue bandwidth shape 5 0 0 0
srr-queue bandwidth limit 50
On 3750, the bandwidth for queue 1 is limited to 100mbps x 50% / 5 = 10mbps
On 3560, the bandwidth for queue 1 is limited to the smaller value of BW / shape weight and BW x limit%.
Does it sound about right? is there a way to check for mls qos input queue drops? The show mls qos interface xxx stat only shows the output queue drops. Maybe for some reason the input queue never drops?
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Jul 4, 2012
A check out a network segment and want to know why SwA has a static route to SwB if SwA already has a Default GW to Core?
(SwA, SwB - Catalyst3560, Core - Catalyst4948)Note, there are distribute list on SwA - it does not has any OSPF route (exclude O*IA).
Does this mean when SwA send out packet with DA 10.5.64.0/26, Core will use only L2 switching (instead of L3)? Is this more effectively for Core Switch?
Pleace check my reasoning:
1. When use a static route: SwA receive packet from Vlan 20 with DA 10.5.64.0/26 it will strip out Dest. MAC and replace it with MAC of SwB. Core will switch this packet to SwB based on mac add. table (l2 switching)
2. When SwA has only Default gateway and receive packet from Vlan20 with DA 10.5.64.0/26 it replace Dest. MAC with Core MAC. Core receive this packet, lookup route table for 10.5.64.0 entry and forward packet base on this.
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Nov 6, 2011
i have an 2921 connected to an Catalyst 3560. My router interface shows quite a lot of input queue drops. Load is not too much max 5/255.
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Apr 12, 2012
Would like to impliment VLAN's on Cisco IOS Software, C3560 Software (C3560-IPSERVICES-M), Version 12.2(25)SEB4...But I need a DHCP Realy to my Windows Based DHCP Server. How do I enable DHCP Relay on the 3560?
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Jan 10, 2013
I've been fighting what seems to be an increased number of outqueue drops on our core stack and edge switches for the last 3 or 4 weeks.(The core consists of a stack of 5 3750s in 32-gig stack mode. The wkgrp switches are 3560s. all are at 12.2.52) The wkgrp switches are directly connected to users. We use Nortel IP phones with the phone inline with the user PC. auto-neg to 100/full. [code] However I have tried turning off QOS on a couple of workgroup switches (no mls qos, but left individual port configurations the same) but am still seeing drops.Since I have disabled qos on the switches in question (no mls qos) (not the core tho) I am presuming these commands have no affect on the switch operation and therefore cannot be related to the problem. With QOS turned off one would presume that it is general congestion - especially at the user edge where busy PC issues might contribute. So I wanted to see if I could see any instances of packets in the output queues building up.
I wrote some scripts and macros that essentially did a snapshot of 'show int' every 20 seconds or so, and looked for instances of 'Queue: x/' where x was greater than zero.What I found after several days of watching the core stack, and a few of the workgroup switches that are most often displaying the behavior, was that I NEVER saw ANY packets in output queues. I often saw packets in Input queues for VLAN1, once in a great while I would see packets on input queues for fa or Gi interfaces, but NEVER on output queues. [ code] Additionally, when I look (via snmp) at interface utilization on interfaces showing queue drops (both core and wkgroup), they are occurring at ridiculously low utilization levels (as low as 4 to 8%). I've tried to look for microbursts between the core and a wkgroup switch where the core interface was experiencing drops, but haven't seen any (using observer suite). [code] While the queue-drop counts aren't critically high at this point, they are happening more frequently than in the past and I would like to understand what is going on... In most cases, no error counters are incrementing for these interfaces. Is there some mechanism besides congestion that could cause output queue drops?
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Oct 12, 2011
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.
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May 25, 2012
I have made a topology by using one 3560 switch and 2 2950 switches. I have also made 2 vlans name Clients and other Servers and vlan 1 is for anagement purposes. The left 2950 switch is for clients and the right is for servers. Clients is vlan 2 and servers is vlan3 . Now what i want is that my dhcp is should assign ips to clients in vlans 2 provided that servers are in vlan 3. I am also using a border router and i have introduced a default route on the 3560 to the border router.
Now when i assign static ips to my clients pc and server dhcp then i can ping between vlans but when i try to assign ip through dhcp then it wont work. Also the default route on the switch to the border router doesnt seem to work. I can ping only the border router when i put a default route on the border router instead of the 3560 switch.
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Jul 23, 2012
I have a cisco 3560 24PS and its connected to two ADSL broard band routers.one is a personal broadband line using a Billion ADSL broadband router, and the other is a business broardband line using BT's 2wire broadband line.on the Billion routers i have various things attached like a NAS and a printers, both wired connections. then i have laptops and phones that connect over wifi, so its configured to act as a DHCP server
the only thing conncted to my 2wire router is my company's laptop (wired or wifi depending on where i'm working from), so again i have it working as a dhcp server.The switch is configured with multiple vlans, with dhcp scopes assigned for each vlan.I have a static route pointing all traffic to my Billion ADSL for internet connectivity.
The problem i'm having is that when i turn on the cisco switch, all wifi conected devices loose their conection. only 2 things get it working again, a reboot of the router, or disabling then enabling the DHCP service on the router.upon further analysis i was able to find out that the devices were not able to pick up an address from the router. again i looked deeper into this and i can see the following on logs of my router: [code]
so it seems that the router tuns off its DHCP capabilities because it detects that my Cisco switch is running DHCP services. I need to figure out how to keep the billion routers DHCP running when ever the switch is turned on.is there a way of filtering out any DHCP chat from the switch to the router?
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Jan 18, 2013
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.
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May 1, 2013
We are moving a small network of 3560 and 3750X switches from VTP Server and Client to VTP Transparent. I noticed the vlan database is stored differently depending on the VTP mode.
Is there any chance of losing vlan database on a given switch when moving from Server or Client to Transparent?
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Jan 16, 2013
I have two WAP4410N plugged into my Catylist 3560 switches.One of these switches is my Default Gateway for the LAN.The only way I can get a device to connect to the WAP4410N is by assigning it a static IP. Then it works perfectly.
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Jan 3, 2012
I want to implement port-based and MAC-based in these two switches: 2960 & 3560 (both of them have this IOS version: 12.2(55)SE1). And I haven't found a way to implement both of them at the same time. This is what I got:
ip dhcp use subscriber-id client-id
ip dhcp subscriber-id interface-name
ip dhcp excluded-address 192.168.0.0 192.168.0.2
ip dhcp excluded-address 192.168.0.251 192.168.0.255
[code]....
With this configuration I can use port-based, but not MAC based. If I remove the first two lines and change the last line for this one:
address 192.168.0.7 client-id 0112.ae1d.af58.60
Then, the computer with that MAC address got the correct IP, but then the port-based doesn't work. Also, I got this line in the interface what I want to use MAC-based:
ip dhcp server use subscriber-id client-id
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Mar 19, 2012
can you enable dhcp service on a 3560 switch.
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Apr 26, 2012
I'm attempting to configure a Catalyst 3560-X Switch to act as a DHCP Server. There is documentation that supports this feature. Below is my config procedure however after the completed procedue no IPs are handed out to clients. [code]
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Apr 29, 2012
we have a 3560 switch configured with EIGRP with dhcp. We have a user that we cannot ping, however the interface show up / up and no errors on interface. the ip address is 10.2.0.199 - however we have dhcp configured to exclude the range from dhcp ip dhcp excluded-address 10.22.0.1 10.22.0.200 how can this work station get a dhcp address if we have that ip range excluded from the dhcp pool?
The user is off a different switch that is a uplink to this distribution switch. Traceroutes shows that the problem is with the distribution switch.
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Feb 2, 2013
I used to use a CentOS self-made server for intranet for my little office, but I bouth few days ago a Cisco 861 router to replace the linux box.
1. I have 2 public IP classes from my ISP. 1 class is limitted to 80mbit upload, the other to 30mbit upload. So I need some sort of DNAT to be able to know exactly which intranet computer uses big internet and which one limitted internet.
2. I need DHCP server and with static IP addresses (one computer must always have the same IP address, etc).. i have my needs for this.
3. Also I need external access to some servers inside (web, ftp, etc) [code]
So far so good, all looks simple and I can achieve this in 2 hours on a centos linux box (correct routes, ip forwarding enabled and few iptables rules for NAT/SNAT/DNAT).
But on this brand new Centos router well, i'm not even successful in pinging the outside world, nor the inside world I'm tired of reading the forums, the documentation..i want (at first) a simple scenario: vlan+dhcp, fa4 with 1 public ip address and ACCESS to the real world. I wasn't able to achieve not even that much. [code]
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Aug 8, 2012
I have a Cisco 876 router running 12.4.(15)T5, configured as DHCP client. This works nicely.
A Cisco 886 router, running 15.1 software also works with the DHCP client. This also works but has the following strange beheaviour: In the running-config an ip route 0.0.0.0 0.0.0.0 <dhcp assigned address> appears. Also - some other static routes that are in the config using the dhcp keyword are duplicated with the dhcp-assigned address
Now - when a write mem is done, these dhcp-generated route entry's are stored in the startup-config...
This beheaviour is completely different and VERY unwanted. After a change from DHCP server the config will simply stop working, when a write mem was done at the first DHCP situation.
Should we stop using write mem commands when a DHCP client is active in IOS? Is it a bug? Is it a feature?
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Sep 25, 2012
My Network Layout is as, Firewall (with Routing)------>Cisco 3560 Switch (L3)------> connected 8 Cisco 2960 switch (L2)----> all users I have configured 20 VLAN's on cisco 3560 switch with Dynamic Pool and Static, Means, 5 Vlan's are Dynamic and remaining are Static Our Company process provides only internet access to existing clients computers. Problem is that, I configured Static VLAN 5 for one of our Client in their seperate room, mean to say, i activated all ports of their room with Static VLAN 5. one day they configured own DHCP server on Windows 2003 Server with same subnet (Same as VLAN5) in their room without any information and now their all computer/ Laptop acquiring ip address Dynamically.
If i have configured Static vlan on that port's then how it is get Dynamic ip from same port's.How to restrict to permit another DHCP server/Service in our premises. I Do not want to give administrative control to Clients to do such kind of thing with LAN.
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Jan 14, 2012
i have a strange issue with an HSRP Setup. I have two (S1+S2) 3560 as Core/Distribution Layer. Inter-vlan routing are enabled on both Switches. S1 and S2 are connected with an ether channel over four fibre ports. S3 -S5 are the (L2) access layer.
Gi0/1 on S1 and S2 are L3 ports, connect to a Linux Firewall.
HSRP is enabled, S1 is the active router and the STP root bridge.
But, my monitoring via cacti show me, that the Gi0/1 on S2 is active, too! But it should not be active? Only if S1 fails, should S2 the active switch.A client from the access ports on S3 - 5 gets traffic from the Internet via Gi0/1 from S2. Gi0/1 on S1 is active too, but will send mostly traffic to the Internet. Why is S2 active and why route it traffic from the Internet to the client?
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Jan 5, 2012
My actual Scenario
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
[code]....
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Nov 11, 2011
I was trying to find if it's possible to add the option for static routes for DHCP clients on Cisco IOS DHCP config mode. I'm looking to add a settings as defined on RFC 3442, like this one, set on ISC DHCPd server:
Global settings:
option rfc3442-classless-static-routes code 121 = array of integer 8;
option ms-classless-static-routes code 249 = array of integer 8;
And for the subnet declaration:
option rfc3442-classless-static-routes 24, 192, 168, 30, 192, 168, 10, 1;
option ms-classless-static-routes 24, 192, 168, 30, 92, 168, 10, 1;
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May 23, 2013
I need to configure public and private wireless access using an ASA 5505 and an Aironet AIR-AP1041N-A-K9. I need to be able to do this via ASDM and http if at all possible. I simply do not have the time to learn hundreds of lines of arcane CLI code. The Aironet connects to the ASA successfully, and receives an IP. I can then connect to the AP wirelessly, but do not receive an IP. I have setup a second SSIDVLAN on the AP, and can't connect to it at all.
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May 17, 2012
I can ping [URL], from the router but not from a client attached to the router dhcp interface(10.1.3.1). When I turn on ip routing I cannot ping at all. Here is the config I have now that can ping the internet from the router.
sh runBuilding configuration... Current configuration : 1191 bytes!! No configuration change since last restart!version 12.3no service timestamps debug uptimeservice timestamps log datetime msecno service password-encryption!hostname
[code]....
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Jun 26, 2012
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.
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May 29, 2012
I have upgraded a C3750G-12S-E to c3750-ipserviceslmk9-tar.122-55.SE5This switch is a distribution layer switch for one of my remote sites. it contains an ip helper-address on the site vlan's SVI.DHCP relay is no longer functioning for client PCs. Static address assignment allows full network functionality. I enabled debug ip dhcp server packet. [code] Actually I am betting you upgraded your IOS from something before 12.2(50)SE to 12.2(50)SE or later. We added enhancement CSCso19800 which will validate DHCP options when we are a relay agent.
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May 7, 2013
I am trying to configure interface vlan1 to get an ip address from dhcp by entering the commnad ip address dhcp ios rejects the dhcp portion of my command as not recognised although it is referred to in Cisco manuals.my IOS version is c2950-i6k2l2q4-mz.121-22.EA14.bin.I get the same problem when I try to configure ip http secure-server on the switch. Is this a known bug or whether I have the correct IOS version for these commands?
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Feb 23, 2012
Haveing issue with DHCP server handing out IP addresses to client connected to VLAN5 interface.ISP Router>Firewall -(WatchGuard Drop-in mode) I have several 3750 switches and one acting as a L3 switch. The L3 is configured as follow: [code]
If I connect a laptop to int fa1/0/10 I DO NOT get an IP address from the 10.100.0.8 scope. If I connect to another interface within the VLAN 1, I get an address from the 10.100.0.0 range.
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Oct 17, 2012
I have been looking at deploying a small core switch design for an important branch office that would consist of 2 cores with an etherchannel link and then 4 POE access switches linked to both cores utilising STP. I will also want static IP routing on the cores and will set up HSRP for gateway failover.
The initial switch I looked at for the core was WS-C3560E-24TD-S however after finding that there is no stock around of this at the moment I have seen the WS-C3560X-24T-S which looks like it will do everything I need including IP routing, HSRP and QoS for VOIP. The thing that concerns me is this is about £1000 cheaper so i'm slightly worried im missing someting.
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Jun 11, 2013
I have two 3560s that i would like to upgrade. But first i would like to make -absolutely- sure i dont wind up in a situation where i have to roll back over a console connection.to the day i still cant understand why oh why someone removed (or chose not to implement it everywhere) tftpdnld from rommon ;)
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Dec 6, 2011
I have one Cisco 3560, and it is connected to Firewall...I already turn on the ip routing, which is able to do interVLAN..In 3560, the static route is 0.0.0.0 0.0.0.0 192.168.2.2
3560 (port 1) =====> Firewall (port 1) ======> Internet (WAN)
192.168.2.1 192.168.2.2
Which mean... anything from 3560 will be rote to Firewall port 1 (192.168.2.2) and all the user behind 3560 will able to connect to Internet (WAN).
I want different setup now, I'm trying to configure another port (port 2) from Cisco 3560 connect to Firewall port 2...
3560 (port 2) =====> Firewall (port 2) ======> Internet (WAN)
10.1.1.1 10.1.1.2
I want subnet 10.1.1.x route to different gateway (10.1.1.2) to Firewall go out to WAN... and not using 192.168.2.2 gateway to WAN.
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May 9, 2012
I start configuring Cisco 2821 router for multicast . First short description and attached sheme explanation. Let we say I have small network with 100 users. One router and Cisco switch 3560. Two VLAN’s, one for data another for multicast. Data from internet works fine but now I want to connect multicast servers (or source of more multicast streams) from another subnet. Router have three interfaces.I expect there should be no problems with multicast configuration, but unfortunately it is not like I expect. What I did ?
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