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DHCP Option-82

nwekechampion
Level 3
Level 3

Hi All,

Can anyone explain what dhcp option-82 is used for?

Like any specific use-cases?

I really do not see the point in using it as I have always had success relaying with out it to dhcp server.

 

Thanks

22 Replies 22

first the op-82 is add from SW or from router (relay)
for SW I explain before the use of class <<- this if need lab I can run 
for Router relay I already finish lab for this case I will share here after 1-2 hrs.

in MPLS SP core you can use DHCP relay with op-82 to provide IP to CE depend on VRF that CE connect to. 

Screenshot (420).pngScreenshot (421).pngScreenshot (422).png

ah, this makes sense now.. depending on VRF.

However in your config I did not see an option-82 entry

Hi @MHM Cisco World ..

I am yet to lab this and test it myself.

As soon as I do, I will update you.

Thank you again!

So Sorry, I see your previous comment, I will share the traffic capture to see OP-82 in real traffic. 
thanks 
MHM 

config of lab 
hostname R5-P-DHCP
!
boot-start-marker
boot-end-marker
!
!
!
no aaa new-model
no ip icmp rate-limit unreachable
ip cef
!
!
!
!
ip dhcp pool VRF-RED
vrf RED
network 10.0.0.0 255.255.255.0
default-router 10.0.0.1
!
ip dhcp pool BLUE
vrf BLUE
network 11.0.0.0 255.255.255.0
default-router 11.0.0.1
!
!
!
no ip domain lookup
no ipv6 cef
!
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
ip tcp synwait-time 5
!
!
!
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
no ip address
shutdown
duplex full
!
interface FastEthernet1/0
no ip address
shutdown
speed auto
duplex auto
!
interface FastEthernet1/1
no ip address
shutdown
speed auto
duplex auto
!
interface FastEthernet2/0
no ip address
shutdown
speed auto
duplex auto
!
interface FastEthernet2/1
no ip address
shutdown
speed auto
duplex auto
!
interface Serial3/0
ip address 100.0.0.5 255.255.255.0
mpls ip
serial restart-delay 0
!
interface Serial3/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/3
ip address 200.0.0.5 255.255.255.0
mpls ip
serial restart-delay 0
!
interface GigabitEthernet4/0
no ip address
shutdown
negotiation auto
!
router ospf 100
network 100.0.0.0 0.0.0.255 area 0
network 200.0.0.0 0.0.0.255 area 0



R2-PE2#show running-config
Building configuration...

Current configuration : 1678 bytes
!
version 15.2
service timestamps debug datetime msec
service timestamps log datetime msec
!
hostname R2-PE2
!
boot-start-marker
boot-end-marker
!
!
!
no aaa new-model
no ip icmp rate-limit unreachable
ip cef
!
ip vrf BLUE
rd 1:100
!
!
!
ip dhcp relay information option vpn
!
!
!
no ip domain lookup
no ipv6 cef
!
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
ip tcp synwait-time 5
!
!
!
!
!
!
!
!
!
!
!
!
interface Loopback0
ip address 2.2.2.2 255.255.255.255
!
interface FastEthernet0/0
ip vrf forwarding BLUE
ip address 11.0.0.1 255.255.255.0
ip helper-address global 200.0.0.5
duplex full
!
interface FastEthernet1/0
no ip address
shutdown
speed auto
duplex auto
!
interface FastEthernet1/1
no ip address
shutdown
speed auto
duplex auto
!
interface FastEthernet2/0
no ip address
shutdown
speed auto
duplex auto
!
interface FastEthernet2/1
no ip address
shutdown
speed auto
duplex auto
!
interface Serial3/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/3
ip address 200.0.0.2 255.255.255.0
mpls ip
serial restart-delay 0
!
interface GigabitEthernet4/0
no ip address
shutdown
negotiation auto
!
router ospf 100
network 2.2.2.2 0.0.0.0 area 0
network 200.0.0.0 0.0.0.255 area 0




R4-CE2#show running-config
Building configuration...

Current configuration : 1375 bytes
!
version 15.2
service timestamps debug datetime msec
service timestamps log datetime msec
!
hostname R4-CE2
!
boot-start-marker
boot-end-marker
!
!
!
no aaa new-model
no ip icmp rate-limit unreachable
ip cef
!
!
!
!
!
!
no ip domain lookup
no ipv6 cef
!
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
ip tcp synwait-time 5
!
!
!
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
ip address dhcp
duplex full

 

Thanks @MHM Cisco World .. this was really helpful