DHCP-server on switch, but not int on switch as gateway - DHCPD: there is no address pool..

Energia · ‎02-20-2018

Hi, I have configured a dhcp-server on a switch and are trying to configure a ISR4431 by PnP throught the mgtm-interface when it boots up.

Router-----Switch------ISR4431

DHCP-config on the switch:

----------------------//---------------------

ip dhcp excluded-address 192.168.51.1 192.168.51.250
!

ip dhcp pool O-nett-LAB network 192.168.51.0 255.255.255.0

default-router 192.168.51.112

lease 0 0 5

----------------------//---------------------

192.168.51.112 is configured on the router and I do have a trunk connecting them. On the switch I have configured 192.168.51.61 255.255.255.0 int vlan 51.

When I plugg a PC into the switch I do get a lease with gateway, but when I connect the mgmt-interface (Gi0) on a ISR4431 I do not get a lease (at startup/PnP).

Debug shows me this:

Feb 20 22:15:20.949: DHCPD: Reload workspace interface Vlan51 tableid 0.

Feb 20 22:15:20.949: DHCPD: tableid for 150.106.51.61 on Vlan51 is 0

Feb 20 22:15:20.949: DHCPD: client's VPN is Mgmt-intf.

Feb 20 22:15:20.949: DHCPD: using received relay info.

Feb 20 22:15:20.949: DHCPD: Sending notification of DISCOVER:

Feb 20 22:15:20.949: DHCPD: htype 1 chaddr 002a.107d.XXXX

Feb 20 22:15:20.949: DHCPD: interface = Vlan51

Feb 20 22:15:20.949: DHCPD: class id 636973636f706e70

Feb 20 22:15:20.949: DHCPD: out_vlan_id 0

Feb 20 22:15:20.949: DHCPD: DHCPDISCOVER received from client 0063.6973.636f.2d30.3032.612e.3130.3764.2eXX.XXX.662d.4769.30 on interface Vlan51.

Feb 20 22:15:20.949: DHCPD: using received relay info.

Feb 20 22:15:20.949: DHCPD: Sending notification of DISCOVER:

Feb 20 22:15:20.949: DHCPD: htype 1 chaddr 002a.107d.XXXX

Feb 20 22:15:20.949: DHCPD: interface = Vlan51

Feb 20 22:15:20.949: DHCPD: class id 636973636f706e70

Feb 20 22:15:20.949: DHCPD: out_vlan_id 0

Feb 20 22:15:20.949: DHCPD: there is no address pool for 192.168.51.61.

When i configure int gi0 on the ISR4431 with:
no shut
ip address dhcp

It receives a lease the same way as the PC....

Any clues?

Reza Sharifi · ‎02-20-2018

Hi,

You can't use the management interface to connect the switch to the router. The management interface (g0) is a host port and can only be used for out-of-band management. If you want to connect the switch to the router as a point-to-point connection, you need to use a different interface.

HTH

Energia · ‎02-20-2018

The switch is part of the mgmt-network, I am connecting it for mgmt, not for regular traffice, should that not work?

MGMT-ROUTER-----(vlan51)-----MGMT-SWITCH--(gi0/1)------(mgmt-int)--ISR4431

Reza Sharifi · ‎02-20-2018

MGMT-ROUTER-----(vlan51)-----MGMT-SWITCH--(gi0/1)------(mgmt-int)--ISR4431

In the above scenario, the switch in the middle is for management only and both touters (one on each side) use the mgmt interface to connect to the switch and both routers interfaces need to be in the same vlan (51).

HTH

Energia · ‎02-20-2018

Sorry, that was not what I ment.

MGMT-ROUTER and MGMT-SWITCH is not connected through the mgmt-interface, but by regular interfaces with a trunk (vlan 51). Each interface (except uplink) on MGMT-SWITCH are then part of vlan 51 as access ports. The only one connectet by its mgmt-interface is the ISR4431 (that is connected to gi0/1 on MGMT-SWITCH).

As I stated in my first post: If I plugg in a PC or a network device with a DHCP-client I do get a lease from the DHCP-server on the MGMT-switch and the gateway (on the MGMT-ROUTER) is reachable.