Cisco Switching/Routing :: DHCP Options On C1812 Router?
May 1, 2012
I am going to get some wyse thin clients up and running on our departments. Each department communicate with the main-office through Cisco C1812 routers.
In order to get functionally DHCP up and running, I need to
A - Configure some Dhcp options on the C1812 routers
B - Perform a DHCP relay from each department to the main-office
Option B will cause some additional issues, so is not preferred.
The question is: Does the Cisco DHCP-client have an option for configuring DHCP options? I need to put in among others, an option 161, a string value pointing to a ftp-server. Can this be done? And if it can, what is the right syntax
I have recently started working here, therefore I am not certain of the IOS-version on the router, as I still not have the logon-information, but I will aqquire this shortly.
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Jan 13, 2013
I have configured DHCP snooping on a WS-3560G-48PS running IOS 12.2(58)SE2 ipservicesk9 variant.When I enable DHCP snooping clients don't get IP addresses, when DHCP snooping is disabled, everything works fine.I have set up a SPAN port and run a capture (attached) on the traffic. Wireshark notes the Seconds elapsed field appeared to be encoded in little-endian but only on some packets. Apart from that, I can see nothing wrong with the DHCP Offer responses from my DHCP server.Attachment config.txt contains the interesting parts of the configuration. Please note g0/32 has been set to ARP inspection trust as without working DHCP snooping it would require a static bind.Is there any way of figuring out which option can't be parsed? Is there a way to force forwarding of unparsable DHCP packets while still running DHCP snooping?
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Apr 3, 2012
Have a client wanting to hand out public ip addresses to all clients from a PFSense Firewall terminating the internet connection.
How do I allow the Cisco Switches currently in place, configured with private ip addresses in the 10.10.x.x ranges and Vlans, where the main 3550 layer 3 has defined dhcp scopes for each vlan, to relay dhcp requests from all vlans to the PFSense firewall?
I assume I would take off the currently defined dhcp scopes for the vlans and configure each vlan/switch with the ip helper address and specify the PFSense firewall and that Nat would have to be disabled onthe firewall?
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Jun 19, 2012
I have two Routers (C1812 & C1841) each having different version of IOS images. I was wondering if its possible to copy IOS image from flash of one Router and use it to upgrade another.
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Oct 10, 2012
I have 2 Catalyst 2960S (24 ports and 48 ports). Can I stack them using the Uplink connection instead of the stack modules. I know Stack module is the best option but it is kind of expensives (half price of the 24 ports switch) and I only need to stack no more then 2 switches.
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Sep 26, 2012
On occasion employees are downloading large files for business purposes, at very fast speeds. This has the potential to overwhelming our Internet circuits which causes our Customers problems accessing our Web Hosting services.
Our network is comprised mostly of 2960S switches for the employees. Webservers are connected to other 2960(nonS) switches and directly into the 6509 VSS.
Customer’s traffic comes in through one pair of ASA’s.
Employee’s traffic is handled by another pair of ASA’s.
Employee traffic flows from the 2960’s, past an L3 SVI on the 6509, then through the Employee ASA’s, then to the ASR’s, then out to the ISP#1 or ISP#2
Web Server traffic flows from the 2960’s or 6509, to the Customer ASA, then to the ASR’s then out to ISP#1 or ISP#2. Web server traffic does not flow through an L3 SVI.
The goal is to allow employees the ability to have the most bandwidth they can, however customer traffic always has to be preferred in the event of a ISP circuit approaching its limit.
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Jan 16, 2012
I'm troubleshooting a 3750 switch stack problem where computers are showing input and CRC errors. I'd like to be able to execute a "show interface" command that will show me only the line showing the switch port and the line showing the input errors, but so far I can't figure out a way of combining those two parameters.
If I do "show interface | include Ethernet[0-9]�" I get all the lines showing the port numbers:
GigabitEthernet1/0/1 is up, line protocol is up (connected)
GigabitEthernet1/0/2 is up, line protocol is up (connected)
GigabitEthernet1/0/3 is up, line protocol is up (connected)
[Code].....
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Nov 28, 2011
I am looking for a how to configure a DHCP server for a Cisco SMB 300 series switch to obtain an automatic configuration. Currently i am using a Cisco 1800 router as my DHCP server and the DHCP pool serving the 300 series switch is configured as follows.
ip dhcp pool Cisco_SMB_300
network 192.168.0.0 255.255.255.0
default-router 192.168.0.1
[Code]......
Looking at pcaps, I don't even see a tftp request going the server after the switch obtains an IP via DHCP. The config file format is exactly as obtained from the download backup section (pretty sure its not the issue since i don't see a download attempt). Also, the SMB switch is running the latest firmware image (1.1.1.8)
Looking though the admin guide i did not see specifics on how the DHCP server was to be configure for the auto configuration feature to work.
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Apr 30, 2012
I've studied and labeled out MPLS and MPLS VPNs several times. The situation I'm presented with is a little different from most of the case studies I've seen in my MPLS books. I've attached a diagram.
We have a IPsec site to site tunnel from our main HQ router to a Cisco ASA 5510 in the core network in the colo. This allows our HQ office to reach the private sub nets in our core without using a Cisco VPN client. The problem we are running into is that this seems to be putting undue strain on the Cisco 2811. I feel like the 2811 should be able to handle it but doing any kind of upload or download through the tunnel spikes the CPU/Interrupts and makes the router CLI basically stop responding until the traffic transfer is stopped or completed. During this time, certain Cisco SCCP phones on our Broad works platform cycle while the SIP phones on the same platform are OK. We are trying to alleviate the load on the 2811 by setting up a VRF from the HQ network to the private VRF used in the Core for private sub net communication. The problem I'm having is the the HQ also has some public traffic that I do not want to include in the VRFs and would like to have it travel through the P2P circuit we have and access the internet or other public devices through the core public IP Internet routing table.
The flow would be this:
-going to a public address use the public internet routing table
-going to private address in the 10.x.x.x or 172.x.x.x - use VRF to core Private network.
This is a little different of a set up from most of the VRF VPN examples I've seen. Most of those the CE devices is completely private. This is not the case at our HQ.
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Jul 21, 2012
When quoting a Catalyst 3750X with PoE (WS-C3750X-48P-E) the Dynamic Configurator Tool allows to include as the secondary power supply option the Catalyst 3K-X 350W AC Secondary Power Supply (C3KX-PWR-350WAC/2), but the default included primary power supply is the Catalyst 3K-X 715W AC Power Supply (C3KX-PWR-715WAC). My questions are the following:
1. Will this combination of power supply work?
2. Will the C3KX-PWR-350WAC/2 be able to power up the switch if the primary power supply of 715W fails?
3. Will the PoE will be lost if the primary power supply fails and only the secondary power supply of 350W keeps working?
4. If this secondary power supply of 350W is not suitable for PoE, why it is available as a secondary power supply option in the Dynamic Configurator Tool for a PoE switch?
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Mar 17, 2012
Got 2 of these switch stacked and there is some changes that we are going to undertake which will require us to utilize the whole 8 or 4 (2 from each switch) SFP ports. Just need some adivce on which particular fiber modules should I procure. Does this switch support 10GB of SFP ?
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Sep 8, 2012
What are the options avilable to add a cat3560 g switch to a stack of 3750x switches.?is there a connector avilable ?or is it possible to trunk via fiber ? cat 3560 has 4 sfps and 224 10/100/1000 ports with poe. cat 3750 stack has a 10 gb up link . What are the possible options?
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Feb 12, 2012
I have a couple of WS-C3750X-48T-L and a couple of WS-C3750X-12S-S, I want to stack all four of them together into a single stack. WS- C3750X-12S-S are running c3750e-universalk9-mz.122-58.SE2 whereas WS-C3750X-48T-L are running c3750e-universalk9-mz.122-55.SE3.I have got a couple of queries as under:What are the options to achieve putting all these 4 switches into a single stack? Can the LAN Base switches upgraded to IP Base?
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Nov 11, 2012
I have some DHCP trouble since I subnetted my network with a 2921. My clinets are in 172.16.2.0/23 and DHCP servers are in 172.16.5.0/24.Sometimes, randomly I guess, I get NACK from my DHCP server, and if I look into DHCP logs I got something like this:
15,11/09/12,09:52:27,NACK,172.16.3.172,switchE51D12.host.com,A0CF5BE51D12,,0,6,,,,,,,,
15,11/09/12,09:52:28,NACK,172.16.3.172,switchE51D12.host.com,A0CF5BE51D12,,0,6,,,,,,,,
15,11/09/12,09:52:29,NACK,172.16.3.172,switchE51D12.host.com,A0CF5BE51D12,,0,6,,,,,,,,
[code]....
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May 12, 2013
I am a newbie to Cisco. I am trying to setup NAT with DHCP in our office on CISCO 819 router. I am having a problem with DHCP not assigning an IP on vlan1. I cannot figure out what i'm doing wrong. Below is my config and debug from DHCP.
router#sh config
Using 4328 out of 262136 bytes
!
! Last configuration change at 05:56:39 UTC Mon May 13 2013 by cisco
! NVRAM config last updated at 05:57:16 UTC Mon May 13 2013 by cisco
[Code]....
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Jan 2, 2013
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...
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Nov 18, 2012
in my simple network setup, I cannot resolve DNS queries from inside my NATted network. On the router I can ping both IP-addresses and names. Ping from the local machine works for IP-Adresses but not for names. When doing nslookup, addresses are not found and a SERVFAIL message is returned. I use a Cisco ISR 861 Router to connect our local LAN to the Internet (The WAN of the 861 is connected to another DHCP/NAT-Router, which in turn connects to the ISP-Modem). Addresses in the local LAN are DHCP-distributed, the DNS-Servers from my ISP are configured on the Router and the DNS-Information is distributed correctly to my local LAN machines (as I can verify by doing nslookup on Linux).
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Jul 9, 2012
Is it possible to configure an 881 router to act as a DHCP server to 4 VLAN's each with a different scopes all through a single ethernet interface?
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May 2, 2012
i'm interested if it's possible to set the NTP server via DHCP on an 2901 Router with 15.2(2) image.
i configured the interface gigabit 0/0 as dhcp client. The DHCP Server sends to me DNS, Default GW and NTP. All is working fine, but the NTP will not be configured. i tried to add an DHCP option request, but there is no NTP (42) value. [code]
is there any way to add the value NTP (42) for the DHCP request or isnt it possible?
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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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Apr 19, 2012
recently we had some performance issues with C2811 which caused us to do some lab testing. For testing we used also C1812. The results were quite surprising for us, as the C1812 appeared to be more efficient than C2811. Below you can see the lab scenario and results.
1. Why C2811 is performing worse than C1812?
2. Is there any official Cisco reference stating what are the max VPN throughputs of certain platforms/models? (we consider migration to C2900 platform and would like to choose the right model)
[URL]
as presented on the small diag:
All routers had enabled onboard hw VPN modules and SEC/K9 IOS ver. Configuration was very simple and beside encryption there were also GRE tunnels configured and EIGRP process for routing between "remote LANs". Part of conf responsible for encryption:
crypto isakmp policy 10 encr aes 256 authentication pre-share group 5 lifetime 3600crypto isakmp key ......... address ......... no-xauth!crypto ipsec transform-set SHA-AES256 esp-aes 256 esp-sha-hmac
crypto map VPN 90 ipsec-isakmp set peer ......... set transform-set SHA-AES256 set pfs group5 match address .........
TEST RESULTS
Cisco 1812Cisco 2811iperf generated BW [bps]WAN if BW (max of 30s avgs) [bps]CPU usage (max of 5s avgs)WAN if BW (max of 30s avgs) [bps]CPU usage (max of 5s avgs)500k--540k5%1M1,1M3%1,2M8%2M2,1M4%2,3M14%5M5,4M10%5,7M34%10M10,6M20%11,5M65%15M15,8M28%17M96%16M--17,2M99%25M27M48%--35M38M64%--45M48,2M72%--53M60,8M88%--59M67M94%--61M72M97%--
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Jul 29, 2012
how can I show the DHCP-range of a router if I don't have privilege level? (not in enable-mode),I can do a "show ip dhcp pool" - this will show me the range which is configured with the network-command.But there are also some dhcp-exclude-addresses which I can't see.... (I did a test on a router with full privilege-access)I need this because I have a router with limited access from our provider.
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Dec 11, 2012
I am running into a DHCP problem on a Cisco 891 running 15.0(1)M2. I am running DHCP on the router and want to reserve an address for a printer. I have done this hundreds of times on hundreds of routers. Per Cisco recommendation, I let the printer lease an address to see whether it uses it's "hardware-address" or "client-id". This printer uses the "hardware-address" format. The printer has leased 10.0.0.102 right off the bat. I want it at 10.0.0.50.
I have a DHCP pool, like this:
ip dhcp pool CLIENT
network 10.0.0.0 255.255.255.0
domain-name chsinc.ds
default-router 10.0.0.1
dns-server 10.0.0.1
lease 2
I create a "reservation" like so:
ip dhcp pool HP_LaserJet_Printer
host 10.0.0.50 255.255.255.0
hardware abcd.ef12.3456
Now I do a "show running-config" to see what I've put in and it looks just like above. Now we reset the network settings or change any network setting on the printer to force it to renew it's lease. What should happen and what usually happens is that the printer should request an IP, be offered 10.0.0.50, accept that IP and come up on that IP address. What is happening with this particular printer is that the printer requests a specific IP (the same IP that it had initially = 10.0.0.102), the router says OK and does not enforce the reservation. Then the router actually deletes the hardware-address config line right out of the running config. A "show running-config" shows that the reservation config now looks like this:
ip dhcp pool HP_LaserJet_Printer
host 10.0.0.50 255.255.255.0
See the logs below. Notice the ones in bold.
000226: Dec 12 17:34:01.382: DHCPD: Seeing if there is an internally specified pool class:
000227: Dec 12 17:34:01.382: DHCPD: htype 1 chaddr 101f.74b0.575c
000228: Dec 12 17:34:01.382: DHCPD: remote id 020a00000ae1e10100000001
000229: Dec 12 17:34:01.382: DHCPD: circuit id 00000000
[code]....
Is there a way to make the router enforce the reservation and not let clients just bring their own IP and actually make changes to the running-config of the router?
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Jan 20, 2012
If it's possible, how do you protect/block a unauthorized DHCP SOHO router with NAT form a Cisco 3750?
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Jan 30, 2011
I have a 3911 router with a 1242 AP. The problem that I have is that when the user is trying to connect, the user get the OS Ip address 169.254.168.154 and I see that when I do the "show dot11 association" command, but when I do sh ip dhcp binding on the router I see
172.19.9.141 0100.18de.74db.14 Jan 31 2011 11:14 AM Automatic
The router is seeing as if the router gave the ip address to the user, but the reality the user was assigne the OS ip address 169. I did "debug ip dhcp server events" and I got the following:
Jan 31 11:09:06.752 EST: DHCPD: Seeing if there is an internally specified pool class:Jan 31 11:09:06.756 EST: DHCPD: htype 1 chaddr 0100.18de.74db.14
Jan 31 11:09:06.756 EST: DHCPD: remote id 020a00000a58218400000000Jan 31
[Code].....
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Apr 10, 2012
I am using DHCP/TFTP to autoconfigure a 3945 router. The router properly obtains an IP address and finds the correct TFTP server. The issue lies in the download of the configuration file from the TFTP server. The router downloads the file, gives the "Ok" message, and prompts you to press Return to get started. When I view the running-config, several commands are missing from the Serial 0/0/0 section (HWIC-2T). If I modify the config file on the TFTP server to use Serial 0/0/1 instead and repeat the process, the configuration file loads without any issues and Serial 0/0/1 has all of the commands.
I also tried moving syntax around in my config file, but the end result is still the same. If I use Serial0/0/0 - I don't get all of the commands. If I use Serial 0/0/1, I do.
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Sep 3, 2012
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?
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Feb 12, 2013
I am configuring DHCP pool for voice vlan on cisco 2921 router.
Here is the setup.
2921 router -> 3750 -> 2960 PoE -> 7942 IP Phone
Router Config
ip dhcp excluded-address 10.146.54.1 10.146.89.50
!
ip dhcp pool VoiceVlan
network 10.146.54.0 255.255.255.0
subnet prefix-length 24
dns-server 10.144.68.32 10.144.68.33
option 150 ip 10.146.68.36
default-router 10.146.54.1
netbios-name-server 10.144.68.32 10.144.68.33
netbios-node-type h-node
[code]....
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Mar 17, 2013
i have a simple router on a stick config which is providing dhcp to a customer SSID. however i don't want employees to stay on it and eat the band width since its open. the lease is set to an hour, is there anyway that i could set it so that once your lease expired it can't be renewed for 4 about 8 hours? I am using a cisco 2600 router in this setup.
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Mar 12, 2013
I have this Cisco 1941 router with two Ethernet ports g0/0 and g0/1. The g0/0 is connected to office LAN with internet access. As my office LAN is DHCP, it will assigned a IP address for g0/0 since this g0/0 is configured as "ip address dhcp". Now my question is that i have a group of 5 pcs, namely PC1, PC2, PC3, PC4 and PC5 that is connected to the switch and one of the ports of this switch is connected to g0/1 of Cisco 1941. Is it possible that let say PC2 and PC3 (both DHCP enabled) could access the internet access from g0/0 and at the same time, the office LAN assigned IP address for PC2 and PC3 automatically?
Office Lan with internet access (DHCP) (Default gateway 10.0.0.1)
|
|
g0/0 (DHCP enable) (DHCP assigned IP address 10.0.0.138)
Cisco router 1941
g0/1
|
|
HP Switch
|
PC1 PC2 PC3 PC4 PC5
Is this operation possible? if possible, how to configure inside the router 1941 to achieve this objective?
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Aug 10, 2011
I disconnected and reconnected the powercable while holding on to the setup button until system, alert, setup go amber. The system led light began blinking green. I waited until one of the leds lights on the ports starts blinking green I then connected the ethernet cable connected to my pc. I made sure my lan connection on my computer was set to dhcp.In the docs claim it should take about 1 minute to grab a new ip address. After a few minutes i check the ipconfig on my pc and I get the apipa address.The setup light on the switch remains green while system is amber. The led for port 1 stopped blinking and remains green.My pc is not grabbing an ip address I don't know what else to do.
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Nov 30, 2011
We are looking to avoid the need to install an additional device in our network as our core 6509s are not being pushed by any stretch. However, we are having an issue getting the 6509 to assign DHCP addresses and perform NAT.
Most interfaces and V LAN's on the 6509 are using public IPs and have BGP routing at the edge. We have a trunk up link coming into the 6509 on a ws-6816 card via a SMF GBIC in slot 9, port 2 that feeds a wifi link where we are looking to provide guest access to our network.
We created 2 V LAN s on the switch 20 and 21. We assigned a private IP and network to the VLAN20 interface and assigned a new public /30 sub net ip to the V LAN 21 interface. The following configuration was applied which I thought was the required configuration based on how we would typically configure ISR routers for the same services...
ip dhcp excluded-address 10.200.200.1
!
ip dhcp pool WiFi_Pool
network 10.200.200.0 255.255.255.0
default-router 10.200.200.1
dns-server 4.2.2.1 4.2.2.2
[ code]...
What am I missing in this configuration? Note that if I create an access switch port for v LAN 20 on the switch and plug a laptop in directly to the 6509, the laptop is unable to receive a DHCP address. If I assign the laptop an address in the 10.200.200.0 /24 range manually, I can ping 10.200.200.1 from the laptop, however, the laptop will not get to the internet as it appears to be failing to perform nat.
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Jan 15, 2013
I have this message "DHCP Timeout"on few cisco IP Phones .try to assign IP manually and it's working fine.. seems DHCP not giving IP's to those.. 6500 have configured as DHCP pool.
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