Cisco Switching/Routing :: DHCP Request Not Being Forwarded By Helper Address Same VRF 6500?

Feb 22, 2013

Version 12.2(33)SXI
 int vlan 1
description client vlan
ip vrf forwarding A
ip address 10.1.1.1 255.255.255.0
standby 129 ip 10.1.1.2
standby 129 timers 1 4
standby 129 priority 105
standby 129 preempt
ip helper-address 10.1.2.20

[code]....
 
dhcp requests are not making it to the dhcp server SAME VRF (ip helper-addres is not doing anything.....)extended vrf traceroutes on udp 67 sourced from vlan2 are fine
 
I am expecting udp unicast packets on port 67 "giaddr" relay packets on the DHCP server generated and sourced by the relay on Vlan1
 
eg. Mar  1 01:59:06.731: DHCPD: setting giaddr to 10.1.1.1
 
This exact setup works in our preprod environment with the same code.Only difference is we run Distributed etherchannel on the 6500's where this doesnt work.
 
Wireshark on the client I can see the requests being sent Going to check it with debug ip dhcp server to check the relay logs out of production hours.
 
I have seen so many people say it IS and ISN'T supported on this version of the code.e.g. [URL]
 
I am aware the helper-adddress should inherit the vrf of the interface ip helper-address vrf command is not supported.The fact it works in the PP environment.... could this be due to the Distributed EtherChanel difference? or just some bug....

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Cisco Switching/Routing :: 4500 / 3560 - DHCP Redundancy - IP Helper Address Point To HSRP?

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.
 
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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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The Ip Address 10.80.18.1 is an secondary IP address of vlan 18 , which is used for Teleprescence.

interface Vlan18  no shutdown  no ip redirects  ip address 10.80.18.252/24  hsrp version 2  hsrp 18    preempt    priority 110    timers  1  3    ip 10.80.18.1  secondary    ip 10.80.18.254
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RP request for local IP address 10.80.18.1 on Vlan18, request from pid: 3834
2012 Nov 12 18:22:07 FRMA_BK1_CSN7K_01-COR %ARP-3-INVAL_HDR:  arp [3829]  Found

[code]....

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Apr 9, 2012

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Device Manager Version 6.1(5)51  
                  
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Aug 10, 2011

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Dec 15, 2012

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I'm trying to configure my C3550 with fast ethernet port 0/48 assigned to vlan 2 in static access mode and SVI vlan 2 configured as dhcp client.
 
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Cat3550(config-if)#ip ad
Cat3550(config-if)#ip address ?
A.B.C.D  IP address 
Cat3550(config-if)#ip address  
 
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If it is a version problem is there any possibility to download upgraded version for free? 
 
Cat3550>sh ve
Cisco Internetwork Operating System Software
IOS (tm) C3550 Software (C3550-I5Q3L2-M), Version 12.1(20)EA1, RELEASE

[Code].....

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Dec 11, 2012

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portfast an dother parameters are intact.

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172.19.9.141        0100.18de.74db.14       Jan 31 2011 11:14 AM    Automatic
 
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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
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[Code].....

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We  have 2 nexus 7010 switches configured with HSRP in the network. For all  the vlans core1 is Master and Core2 is standby. In the current setup we  have external dhcp server and dhcp relay is configured for all the  vlans on Master and standby switch. The setup is running the IOS 5.2
 
Activity Done: During  the Maintainacne activity, we isolated core1 switch in the network by  disabling the vpc/keepalive and all the uplinks from access switch. The  core2 switch was master for all the vlans.
 
Issue observed: It  has been observed that new users were not getting ip address from the  dhcp server. The ethereal capture showed that dhcp server was not  getting the dhcp requests from the core2 switch. We disabled the dhcp  feature in core2 and enabled again with dhcp relay again configured on  vlan interfaces .even after doing this no change was observed in  behaviour. Finally we got core1 back in network by enabling all the  links.
 
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Further Testing

1. For  one of the vlan, core 2 switch has been made primary and for new users  checked the dhcp functionality and it was working fine. The aim was to  identify if anything wrong on core 2 related to dhcp relay

2.Again  we changed the priority for this vlan and made core1 master for the  same. This time we disabled this vlan on core1 and tried new user with  core 2 became master and dhcp functionality worked fine for new user.  Actually in this case we have simulated the same behaviour when we  observed the issue with only difference of VPC was not available during  the issue time as core 1 was isolated form network 
Inputs needed.

Is  there any known behaviour for dhcp functionality when VPC is  unavailable? If we see the test scenario2 (wherein core1 was master for  the vlan and we disable this vlan on core 1 and core 2 was able to relay  dhcp requests for new users in this vlan.) it was actually same as  scenario we observed during issue time..

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