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I want to make 4 PC got DHCP IP address No problem with left side, but right side 2 PC can't get IP automaitic. I think the problem is DHCP Relay. How can I use ip helper-address for subinterface of R2?

s1

 interface FastEthernet0/1
   switchport mode trunk
 interface FastEthernet0/2
   switchport access vlan 11
   switchport mode access
 interface FastEthernet0/3
   switchport access vlan 10
   switchport mode access

s2

 interface FastEthernet0/1
   switchport mode trunk
 interface FastEthernet0/2
   switchport access vlan 20
   switchport mode access
 interface FastEthernet0/3
   switchport access vlan 30
   switchport mode access

R1-DHCP

1.Building configuration...

Current configuration : 1593 bytes
!
version 15.4
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Router
!
!
!
!
!
ip dhcp pool Area-1
 network 192.168.11.0 255.255.255.0
 default-router 192.168.11.1
ip dhcp pool Area-2
 network 192.168.10.0 255.255.255.0
 default-router 192.168.10.1
ip dhcp pool Area-3
 network 192.168.20.0 255.255.255.0
 default-router 192.168.20.1
ip dhcp pool Area-4
 network 192.168.30.0 255.255.255.0
 default-router 192.168.30.1
!
!
!
ip cef
no ipv6 cef
!
!
!
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface GigabitEthernet0/0/0
 ip address 190.168.50.1 255.255.255.0
 duplex auto
 speed auto
!
interface GigabitEthernet0/0/0.20
 encapsulation dot1Q 20
 ip address 192.168.20.1 255.255.255.0
!
interface GigabitEthernet0/0/0.30
 encapsulation dot1Q 30
 ip address 192.168.30.1 255.255.255.0
!
interface GigabitEthernet0/0/1
 no ip address
 duplex auto
 speed auto
!
interface GigabitEthernet0/0/1.10
 encapsulation dot1Q 10
 ip address 192.168.10.1 255.255.255.0
!
interface GigabitEthernet0/0/1.11
 encapsulation dot1Q 11
 ip address 192.168.11.1 255.255.255.0
!
interface GigabitEthernet0/0/2
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface Vlan1
 no ip address
 shutdown
!
router rip
 version 2
 network 192.168.20.0
 network 192.168.30.0
 network 192.168.50.0
 no auto-summary
!
ip classless
ip route 192.168.20.0 255.255.255.0 192.168.50.2 
ip route 192.168.30.0 255.255.255.0 192.168.50.2 
!
ip flow-export version 9
!
!
!
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end

R2

Building configuration...

Current configuration : 1151 bytes
!
version 15.4
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Router
!
!
!
!
!
!
!
!
ip cef
no ipv6 cef
!
!
!
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface GigabitEthernet0/0/0
 ip address 192.168.50.2 255.255.255.0
 ip helper-address 192.168.50.1
 duplex auto
 speed auto
!
interface GigabitEthernet0/0/1
 no ip address
 duplex auto
 speed auto
!
interface GigabitEthernet0/0/1.20
 encapsulation dot1Q 20
 ip address 192.168.20.1 255.255.255.0
 ip helper-address 192.168.50.1
!
interface GigabitEthernet0/0/1.30
 encapsulation dot1Q 30
 ip address 192.168.30.1 255.255.255.0
 ip helper-address 192.168.50.1
!
interface GigabitEthernet0/0/2
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface Vlan1
 no ip address
 shutdown
!
router rip
 version 2
 network 192.168.10.0
 network 192.168.11.0
 network 192.168.50.0
 no auto-summary
!
ip classless
ip route 192.168.10.0 255.255.255.0 192.168.50.1 
ip route 192.168.11.0 255.255.255.0 192.168.50.1 
!
ip flow-export version 9
1
  • The command is ip helper-address but we would really need to see the network device configurations, and you must have routing properly configured. Please edit you question to include all the configurations.
    – Ron Maupin
    Mar 13 at 1:46

2 Answers 2

0

this should be configured via R2.

ip dhcp pool Area-3
 network 192.168.20.0 255.255.255.0
 default-router 192.168.20.1
ip dhcp pool Area-4
 network 192.168.30.0 255.255.255.0
 default-router 192.168.30.1
3
  • In that case, won't R2 become a DHCP server? My goal is that R1 is a DHCP server. Mar 14 at 11:41
  • Have you check if you have properly advertised network on R1 and R2 ? From R1 the network should be advertised network 192.168.10.0 and 192.168.11.0 .
    – Gerald
    Mar 14 at 12:37
  • How to check that? Mar 15 at 0:34
0

Some issues:

  • ip helper-address 192.168.50.2 You've added the router itself as DHCP server. That line needs to go.
  • There's no DHCP relay set up for VLAN 30.
  • Add static routes for the remote networks on each router. As it is, each router only sees the immediately attached networks. Lacking a route, packets for the other networks are dropped.
  • Currently, you've got subinterfaces for VLAN 20 and 30 on R1/Gig0.0.0 (towards R2). That can't work as there's no L2 connectivity across R2. At the same time, the DHCP relay won't work for (seemingly) directly attached IP subnets; also routing won't work properly. You need to remove those subinterfaces.
4
  • R2:S 192.168.10.0/24 [1/0] via 192.168.50.1 S 192.168.11.0/24 [1/0] via 192.168.50.1 R1: 192.168.20.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.20.0/24 is directly connected, GigabitEthernet0/0/0.20 L 192.168.20.1/32 is directly connected, GigabitEthernet0/0/0.20 192.168.30.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.30.0/24 is directly connected, GigabitEthernet0/0/0.30 L 192.168.30.1/32 is directly connected, GigabitEthernet0/0/0.30 Mar 13 at 17:01
  • I set up a static route, but the routing situation in R2 doesn't feel quite right to me, is there a problem here? Thanks! Mar 13 at 17:03
  • If you can ping all IP addresses from anywhere then the routing is working.
    – Zac67
    Mar 13 at 17:27
  • No, PC3 and PC4 can't get DHCP and R2 can't ping PC1 and PC2. Mar 13 at 22:25

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