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Today's Topics:

   1. agent.remote-id matching (Andre Mamitzsch)
   2. Re: Recommendation for redundancy (Tiago SR)


Message: 1
Date: Tue, 6 Mar 2018 22:32:36 +0100
From: Andre Mamitzsch <>
To: Users of ISC DHCP <>
Subject: agent.remote-id matching
Message-ID: <>
Content-Type: text/plain; charset="utf-8"


We are experiencing a problem with matching the agent.remote-id in a DOCSIS 
environment. The CMTS inserts the CM MAC in the agent.remote-id, this id is 
then used in subclasses on the server. I was debugging an issue where the class 
matching did not work -   when inspecting the lease file, I found that the 
agent.remote-id is stored as string ("DNm+SP?) and not as a MAC address as 

I analyzed the MAC address and all values are in the range between 0 and 127:

44 -> 68   -> D
4e -> 78   -> N
6d -> 109 -> m
2b -> 43   -> +
53 -> 83   -> S
50 -> 80   -> P

As a proof, I added a new subclass entry using the string and got a match when 
I restarted the device.

MAC addresses  seem to be converted to their ascii representation if they 
contain only printable ascii values. I suspect that it has something to do the 
the ?isascii? and ?isdigit? checks in common/options.c, beginning in line 1828.

I have tested agains 4.3.4 and 4.3.6P1 - both show the same behavior. I believe 
 that we had a similar issue with "hardware ethernet <MAC>?, but this was years 
ago and I? m not sure. I was searching  the bug reports and the mailing list 
but were not able to find anything similar - so any hints or advises are 
welcome !



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Message: 2
Date: Tue, 06 Mar 2018 19:34:51 -0300
From: Tiago SR <>
To: "Users of ISC DHCP" <>
Subject: Re: Recommendation for redundancy
Content-Type: text/plain; charset="UTF-8"

My suggestion may also work if you have a centralized leases database, which 
both servers query (directly or via Radius) to assign addresses.

 ---- On Tue, 06 Mar 2018 16:08:25 -0300 Simon Hobson <> 
wrote ---- 
 > Tiago SR <> wrote: 
 > > If you make use of DHCP Relay or can implement it, you could get the 
 > > servers failover by VRRP, IP SLA, OSPF, etc. 
 > > The DHCP Relay would query a DHCP Server IP address that would 
 > > automatically point to secondary server in case of primary going down. 
 > The problem with that is that unless you use the failover protocol then you 
 > cannot easily have a seamless handover - this is NOT a stateless server like 
 > a web server serving static pages. The standby server must AT ALL TIMES have 
 > a completer and up to date copy of what the master server has - that is not 
 > easy to do without using failover. If the backup server does not have a 
 > complete and accurate copy of the primary server's lease database then you 
 > will suffer from one or more potentially serious problems. 
 > Once you use failover to manage syncing the leases to the backup, then you 
 > might as well just use failover to manage availability. 
 > _______________________________________________ 
 > dhcp-users mailing list 


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