Cisco Switching/Routing :: RFC 951 Why DHCP Option Has Magic Cookie

Oct 27, 2011

In RFC 951, the format of BOOTP packet was legislated, but the vendor information was not legislated in this document,  so the authors of this document had described that :"If the 'vend' field is used, it is recommended that a 4 byte 'magic number' be the first item within 'vend'.  This lets a server determine what kind of information it is seeing in this field. "
I think it meant that the format of vendor information wasn't fixed in RFC 951, and any vendor can legislate a new format of vendor information by itself. And the value in "magic cookie" can be set by any vendor.But in RFC 2131, the format of DHCP packet was legislated, and the "magic cooke" was fixed to values 99, 130, 83 and 99, I think it meant that the format of option information in DHCP packet was fixed absolutely and any vendor can't legislate a new format by itself.
Since the format of option information in DHCP packet was fixed absolutely, why the network device needs "magic cookie" to  identify the mode in which the succeeding data is to be interpreted ?  I think the magic cookie is not useful in DHCP packet because the format of option information is fixed. In other words, there is only one format of option information forever.

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Cisco Switching/Routing :: 3550 / 2950 DHCP Relay Option To Router Handing Out DHCP

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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Cisco Switching/Routing :: Adding Dhcp Option 82 On C2960S

Dec 12, 2012

I have a very simple setup containing 3 C2960S switches:switch 1:  central switch, acting as router between VLAN 1 en VLAN 2switch 2+3: edge switches, connected via 1 link to central switch, both on VLAN 2,Clients connect to switch 2 and 3 using dhcp, switch 1 uses dhcp relay to forward requests from VLAN 2 to the dhcp server on VLAN 1.  So far so good.Now I want switch 1 to add option  82 to the dhcp requests so the dhcp server can see whether the request came through switch 2 or switch 3. I tried turning on dhcp option 82 support on switch 1 by doing.

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Cisco Application :: ACE4710 Insert Cookie - Does It Overwrite Server Cookie

Mar 28, 2012

I was trying to implement stickiness based on cookie. Server inserts a cookie and sends it to the browser. I learned from app team that this cookie is changing dynamically during the session, so stickiness based on server’s cookie doesn’t work.
Now I want to investigate into possibility of ACE to insert a cookie. My question is: ACE feature of “cookie insert”: does it add additional cookie into http header without removing server cookies or it deletes the cookie(s) that server put into http header and replaces them with its own cookie?

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Protocols / Routing :: Can't Find DHCP Lease Option In Nano-station Settings

Jan 25, 2013

I own a Nanostation5 Loco, and I have a router behind it.I would like to add a DHCP Lease to that router and do a port forward to the router.I can not find the DHCP Lease option in Nanostation settings, but if I choose to see DHCP Leases in "Extra info" on main page I can see some MAC and IP addresses there.When it comes to port forwarding, I fill the form slots with info, and when I press OK to save it a pop-up comes saying "Please fill out this field", a field for another forward rule.

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Cisco Switching/Routing :: Option For WS-C3560X-48T-S

Jul 16, 2012

Im trying to find an affordable Cisco switch with similar capabilities and features as the WS-C3560X-48T-S (L2/L3 routing as in IP Base, dual power supply, etc.).

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Cisco Switching/Routing :: How To Use USB Option On 2960s

Nov 5, 2011

just got new hardware and decided to try the newer USB port for IOS upgrades. I could not get the switch to recognize my 2gig flash drive. Do I need a proprietary stick or special format?

I also noticed when I removed it the switches crash dump and rebooted?

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Cisco Switching/Routing :: SG300-52 - CLI Configuration Option

Dec 10, 2012

I am trying to configure Cisco SG300-52 switch for the first time and stuck without CLI configuration option. The configuration can be done using GUI, however, configuring using CLI would be more comfortable (as I am used to work with CLI of other Cisco switches)..
I was able to lo gin to switch using SSH, but the CLI appears in MENU format and was not able to find any way to go to CLI mode.
As per some blogs, in SG300 switches CLI mode can be accessed using Ctrl + Z in Menu, which did not work either in my case.
Switch is running with latest firmware version Sx300 Firmware Version

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Cisco Switching/Routing :: 4948 No Option For X-modem

Sep 19, 2012

I am updating the iOS for a 4948 the bootflash is empty so all i can get into is the rommon. There is no option for x-modem. How can I put the iOS onto this device? [code]

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Cisco Switching/Routing :: IOS Upgrade Option In 2960S Switch

Dec 11, 2012

We  have a Cat2960-S Series PoE+ currently running 12.2(55) SE5 ios with SW image C2960S-UNIVERSALK9-M.We want to upgrade the ios to the lastest version but found there are 2 version: 12.2(53) SE2 and 15.0(1) SE.Which is the best & suitable for upgrade?

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Cisco Switching/Routing :: 4507R+E / SSO Not Available As Redundancy Mode Option

Oct 31, 2012

Why rpr is the only available redundancy mode option available to me.  I'm running a 4507R+E with twin SUP7-E's.
Abbreviated show ver Cisco IOS Software, IOS-XE Software, Catalyst 4500 L3 Switch Software (cat4500e-UNIVERSALK9-M), Version 03.03.01.SG RELEASE SOFTWARE (fc2)Technical Support: [URL]/techsupportCopyright (c) 1986-2012 by Cisco Systems, Inc.Compiled Sun 26-Aug-12 13:45 by prod_rel_team
ROM: 15.0(1r)SG2gp08401 uptime is 6 weeks, 6 days, 4 hours, 59 minutesUptime for this control processor is 6 weeks, 3 days, 2 hours, 21 minutesSystem returned to ROM by RPR SwitchoverSystem image file is "bootflash:/cat4500e-universalk9.SPA.03.03.01.SG.151-1.SG1.bin"Jawa Revision 7, Snowtrooper Revision 0x0.0x1C


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Cisco Switching/Routing :: N7000 Inter-AS L3VPN Option B

Nov 29, 2012

I ran into problem with design that was prepared for Catalyst 6500, but in the meantime infrastructure got upgraded to Nexus. I have two datacenters connected with 1Gbit line (point-point), both ends of this circuit are N7K. There are few segments (like LAN, DMZ, PUBLIC) in separate VRFs in each DC and intention was to carry over these segments between locations using VPNv4 exchange via BGP. Each location have its own AS number and IPv4 BGP session is running between them (for global routing table at the moment). I tried to add VPNv4 to that peering session, but got message it is not supported in NX-OS for eBGP. Tried to find some more info about such limitation, but failed.
Before I start explore other options like Option A (creating subinterfaces per VRF and running separate IPv4 BGP session in each).

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Cisco WAN :: 2811 Router - DHCP Option 60 / 43 On IOS To Aruba AP

Oct 3, 2011

I'm trying to configure my Cisco Router 2811 which is also acting as the DHCP server for my branch office for DHCP option 60 and 43 so Aruba AP's at my branch can discover it's master Controller? What is the command I need to enter in the Cisco router?

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Cisco Routers :: RV042 - How To Setup DHCP Option 66

Oct 13, 2012

I need DHCP Option 66 to be enabled my small business RV042 router, so the IP phones could know where is the TFTP server.

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Cisco Routers :: Configure DHCP Option 150 On RV220?

May 3, 2012

Is it possible to configure DHCP option 150 on the RV220?  I have a Cisco 7940 IP phone that is trying to connect back to my office. The VPN is up and I can ping the relevant server but I can't see any way to configure the DHCP option.

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Cisco Routers :: RV042 / How To Configure Some DHCP Option

Jun 19, 2012

I have a RV042 VPN Router with the latest firmware v4.2.1.02.This Router is connected to the main site by a VPN Tunnel.
Now, I like to configure some DHCP Option so I can put a IP Phone behind the RV042. The IP Phone should receive a IP by DHCP from the RV042 and of course, the IP of the Call Manager with the Option 150.
I can configure DHCP and it works fine but I can't find where I have or can configure Option 150.

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Cisco Switches :: DHCP Option 82 On SG-300-10 Port Switch

May 5, 2013

I have sample lab    dhcp-client  ------- (vlan62) sg-300 switch  (vlan62) ------ dhcp server
When I set on switch :
dhcp relay  : enable
option 82 : enable
dhcp server address: ip of dhcp
When debug packets from client to server, there is no 82 option in dhcp discover packets. I mirror all traffic to mirror port with wireshark. I can see dhcp packets but without option 82.
Firmware version:

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Cisco Switching/Routing :: 6500 - Changing LACP Loadbalancing Option

Oct 30, 2012

we have 6500 series switches by default all port channel loadbalancing is src-dst-ip.Now we have a requirement to change LACP load balance method to src-dst-port.
1) If we change LACP loadbalance method whar are the effects we are going have on our core network and all the existing servers

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Cisco Wireless :: 5500 / Dhcp Proxy Option In Controller?

Jul 2, 2012

While configuring a 5500 wireless controller, i came across this option of DHCP proxy under Advanced tab of Controller Option.It asks for the dhcp option 82 remote id format & the dhcp timeout.
1. What is the significance of this & when do we use it?

2. Also, under each wlan ssid that we create, there is an option of dhcp address required under the advanced tab. Do we need to use this option, if we are defining a normal dhcp pool in our controller for that ssid.

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Cisco Switching/Routing :: C3560G-48 - IOS Version Option Or Not Supported On Hardware Platform

Feb 6, 2012

We have 2 x C6506E and 2 x C3560-48's, they are all interconnected via port channels at 2Gb per channel. The 6506's are running CEF but the 3560's are not (The 3560's carry all our server traffic).When I do a show CEF on the 3560's it says %IPv4 CEF not running. There does not appear to be a global command to enable CEF on these switches.Is this an IOS version option or is not supported on the hardware platform?

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Cisco Switching/Routing :: 4507 - Dot1q Encapsulation Option Not Showing Up Under Interface

Jun 9, 2012

I am trying to configure a 4507 R chassis with Dual SUP but i cannot see teh switchpot mode trunk encapsulation dot1q?
I have typed:
interface GigabitEthernet5/1
description DOWNLINK toxxxxxx
switchport mode trunk
channel-group 11 mode on
I have have searched all other commands and sub-commands but could only find dot1q-tunnel which I beleive is for QINQ or some QoS featues and lot for L2 encapsulations?
the puzzling is:
XXX-Core4507#sh int gi5/1 trunk
Port        Mode             Encapsulation  Status        Native vlan
Gi5/1       off              802.1q         notrnk-bndl   1
when I connect the dostribution switch a 3507 to this int gi 5/1, both interfaces do come up?

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Cisco Switching/Routing :: 3750x Remove Stacking Option On Sunday For Testing

May 2, 2013

is it easy to remove the 3750x stacking?  i'd like to test one of them on a sunday and keep the other one on production.  it's just two stack of 3750x, is it hard and do i really need to remove the cables on the back?
basically i need to put a different config for my testing, i gues i need to remove the cables right?  and put it back on the stack before monday.

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Cisco Switching/Routing :: 2921MS DHCP NACK With DHCP Relay?

Nov 11, 2012

I have some DHCP trouble since I subnetted my network with a 2921. My clinets are in and DHCP servers are in, randomly I guess, I get NACK from my DHCP server, and if I look into DHCP logs I got something like this:


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Cisco Wireless :: WLC 5508 - Separate DHCP Server Required To Get Option 43 Setup Properly?

May 7, 2012

I am using a WLC 5508 and its internal DHCP server. I cant find anywhere I can setup option 43. However, the access points are connected in just fine. Do I need to worry about setting up a seperate DHCP server to get option 43 setup properly?

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Cisco Wireless :: 5508 - DHCP Option 43 For 1130 And 1300 Lightweight Access Points?

Mar 14, 2013

I have Cisco 1131 & 1300 Light Weight Acces Points and I have 5508 WLAN controller.  If i enable the wlan controller internal DHCP Server can this access points will work with this internal DHCP server or do i need to configure DHCP option 43 for these access points?  Can these access points works with LWAPP or do i need to configure CAPWAP?

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Cisco Wireless :: AP 1130 - Possible To Active Option DHCP Server In Ap 1130 Dispositive

May 12, 2012

I convert IOS Cisco AP 1130 LAP to 1130 Autonomous mode. Well, the periphericals - clients connect to SSID AP no recieved I.P Adress, I think that is not possible active option DHCP server in AP 1130 dispositive. In mode I.P static clients the connection is established successfully.

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Cisco Application :: Cookie Insert On ACE20-MOD-K9

Nov 13, 2012

We are using an ACE engine module(ACE20-MOD-K9) provide loading balancing service for two WEB servers and configured cookie for stickness. Below is the current configuration and it seems working fine now.
The problem I was facing is before use parameter-map change the http header length to 8k the stickness doesn't really working properly. User complains that their working session constantly be kicked out and redirect them to login page. By tracing traffic from a client we found that sometime ACE fails or stop insert the configured cookie, after increase the header length ACE start getting work.
how does the header length setup effect ACE to insert a cookie? Will the cookie insert attmpt fail if the header is longer then the maximum length configured on ACE? [code]

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Cisco Application :: Ace20-MOD-K9 Cookie Persistency On Ace Module

Sep 5, 2012

I have an ACE20-MOD-K9 with version  A2_3_6a, and i am having problems in cookie persistency. the setup contains 4 servers using round-robin algorithm and cookie persistency and that receive http traffic on port 9090. I have been receiving complains that the users are getting disconnected randomly while accessing the web application through ACE. Below is part of the config, when setting the timeout of the cookie to default or something equal to hours, the disconnection/complains gets worse.

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Cisco Application :: ACE 4710 Cookie Based Stickiness

Jul 23, 2012

We have ACE 4710, It is configured with IP based stickiness and working fine for a web application server (BMC Remedy). We tried configuring cookie based stickiness for the same server. Server application is having JSESSIONID.But after configuring cookie based stickiness, there is an issue that the first page is coming for entering login credentials and after entering it the page is blank or not responding.  What is the pre-requirement for configuring cookie based stickiness in ACE for BMC Remedy web application and which type of cookie based stickiness is suitable or possible?

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Cisco Switching/Routing :: DHCP For PC At G0/1 From G0/0 For 1941

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                                      
                                                        g0/0 (DHCP enable) (DHCP assigned IP address
                                                                                 Cisco router 1941
                                                                                  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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Cisco Switching/Routing :: Ce 500 Cannot Get Ip Address From Dhcp

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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Cisco Switching/Routing :: 6509 - NAT / DHCP

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
ip dhcp pool WiFi_Pool
[ 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 /24 range manually, I can ping 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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Cisco Switching/Routing :: 819 Router - NAT With DHCP

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

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