DHCP offered, but not bound

plani · Thu Jan 14, 2021 8:21 pm

Hi all,

I got an issue running a DHCP-Server on my RB3011 and would apreciate an idea where or what to look for. What I have done so far:
- Setup is Router RB3011 ---- Switch1 ---- Switch3 ---- Cisco Phone
- Set up VLANs according to pcunites tutorial an help as described in my previous thread
- VLAN works, IP-Networks work, Routing between network works, everything fine so far.
- DHCP-Server per VLAN set up on the Router, execpt for VLAN10
- in VLAN10 there is a PiHole running as DNS and DHCP-Server

What happens: When plugging in the CiscoPhone CP7941 to a VLAN70 access-port on switch2 the DHCP-Server for VLAN70 reacts and offers a lease:

[admin@CoreRouter] /ip dhcp-server> lease print detail 
Flags: X - disabled, R - radius, D - dynamic, B - blocked 
 0 D address=172.28.170.199 mac-address=00:23:5E:19:3D:92 
     client-id="1:0:23:5e:19:3d:92" address-lists="" server=dhcp-LAN70 
     dhcp-option="" status=offered expires-after=10s last-seen=20s 
     active-address=172.28.170.199 active-mac-address=00:23:5E:19:3D:92 
     active-client-id="1:0:23:5e:19:3d:92" active-server=dhcp-LAN70 
     host-name="SEP00235E193D92"

After 30 seconds, it disappears, sometimes stays another 30 seconds but latest then it disapears. I also tried to set a DHCP-Option, but to make sure that this doesn't call a problem, I removed it again. Also changing "authoritative=after-2sec-delay" didn't help. The bridge is configured with protocol-mode=none.
Here the exports and config I believe are relevant:

/ip dhcp-server> export
# jan/14/2021 19:15:35 by RouterOS 6.48
#
# model = RB3011UiAS
[usera@Router]/ip dhcp-server
add address-pool=MGMT_POOL disabled=no interface=MGMT_IFACE name=MGMT_DHCP
add address-pool=pool-LAN70 authoritative=after-2sec-delay disabled=no \
    interface=IFACE_VLAN70 name=dhcp-LAN70
add address-pool=pool-LAN100 disabled=no interface=IFACE_VLAN100 name=\
    dhcp-LAN100
add address-pool=pool-LAN200 disabled=no interface=IFACE_VLAN200 name=\
    dhcp-LAN200
add address-pool=pool-LAN300 disabled=no interface=IFACE_VLAN300 name=\
    dhcp-LAN300
/ip dhcp-server network
add address=172.28.56.0/24 dns-server=192.168.2.220 gateway=172.28.56.254
add address=172.28.57.0/24 dns-server=192.168.2.220 gateway=172.28.57.254
add address=172.28.58.0/24 dns-server=192.168.2.220 gateway=172.28.58.254
add address=172.28.99.0/24 dns-server=192.168.2.220 gateway=172.28.99.254
add address=172.28.170.0/24 dns-server=192.168.2.220 gateway=172.28.170.254
[usera@Router] /ip dhcp-server> /ip pool print 
 # NAME                                         RANGES                         
 0 MGMT_POOL                                    172.28.99.100-172.28.99.110    
 1 pool-LAN70                                   172.28.170.100-172.28.170.199  
 2 pool-LAN100                                  172.28.56.100-172.28.56.199    
 3 pool-LAN200                                  172.28.57.100-172.28.57.199    
 4 pool-LAN300                                  172.28.58.100-172.28.58.199    
[usera@Router] /ip dhcp-server> 
[usera@Router] /ip dhcp-server> /interface bridge print 
Flags: X - disabled, R - running 
 0 R name="bridge" mtu=auto actual-mtu=1500 l2mtu=1598 arp=enabled 
     arp-timeout=auto mac-address=48:8F:5A:EA:01:35 protocol-mode=none 
     fast-forward=yes igmp-snooping=no auto-mac=yes ageing-time=5m 
     vlan-filtering=yes ether-type=0x8100 pvid=1 frame-types=admit-all 
     ingress-filtering=no dhcp-snooping=no

Any idea what I did wrong?

Update: I just disabled the DHCP-Server on the PiHole (other VLAN and Network) but makes no difference.

plani · Sat Jan 16, 2021 8:46 pm

Problem solved. I found this or similar issues several times without stating a solution. Maybe because the issue was in front of the keyboard, so here my resolution that might help others:

I forgot to put that VLAN on the trunk-port on the switch in the middle. So the client send a request to the DHCP-Server within the correct VLAN and this request was recieved by the DHCP-Server, as I have no ingress-filtering or anything active yet. The DHCP-Server in return replies to the client, but the reply never reaches the client as is simply just not forwarded on the switch in the middle....

Hope that helps somebody, otherwise, topic closed. Sorry.

DHCP offered, but not bound [SOLVED]

DHCP offered, but not bound

Re: DHCP offered, but not bound [SOLVED]