[j-nsp] JUNOS BootP-relay Behaviour

[alain.briant at bt.com]

Thanks for your answers, but like I told you the JTAC admited that the implementation done on JUNOS on the M series is the correct one.

Buy the way on the EX the VPN keyworkd doesn't exist:

--- JUNOS 9.4R1.8 built 2009-02-08 16:30:58 UTC
Alain at Switch_EX3200> set forwarding-options helpers bootp ?
Possible completions:
+ apply-groups         Groups from which to inherit configuration data
+ apply-groups-except  Don't inherit configuration data from these groups
  client-response-ttl  IP time-to-live value to set in responses to client (1..255)
  description          Text description of servers
> dhcp-option82        Configure DHCP option 82
> interface            Incoming BOOTP/DHCP request forwarding interface configuration
  maximum-hop-count    Maximum number of hops per packet (1..16)
  minimum-wait-time    Minimum number of seconds before requests are forwarded (0..30000)
  relay-agent-option   Use DHCP Relay Agent option in relayed BOOTP/DHCP messages
> server               Server information
[edit] 

Kind regards
Alain


-----Message d'origine-----
De : Daniel.Hilj at synetrix.co.uk [mailto:Daniel.Hilj at synetrix.co.uk] 
Envoyé : lundi 9 mars 2009 15:41
À : p.mayers at imperial.ac.uk; Briant,A,Alain,JPECS R
Cc : juniper-nsp at puck.nether.net
Objet : RE: [j-nsp] JUNOS BootP-relay Behaviour

Try the "vpn" keyword. That's how you change this behaviour with JunosES at least, haven't got a EX to test on now but possibly the same.

set forwarding-options helpers bootp ?
Possible completions:
+ apply-groups         Groups from which to inherit configuration data
+ apply-groups-except  Don't inherit configuration data from these 
+ groups
  client-response-ttl  IP time-to-live value to set in responses to client (1..255)
  description          Text description of servers
> interface            Incoming BOOTP/DHCP request forwarding interface configuration
  maximum-hop-count    Maximum number of hops per packet (1..16)
  minimum-wait-time    Minimum number of seconds before requests are forwarded (0..30000)
  relay-agent-option   Use DHCP Relay Agent option in relayed BOOTP/DHCP messages
> server               Server information
  vpn                  Enable vpn encryption


Regards
Daniel

-----Original Message-----
From: Phil Mayers [mailto:p.mayers at imperial.ac.uk]
Sent: 09 March 2009 12:03
To: alain.briant at bt.com
Cc: juniper-nsp at puck.nether.net
Subject: Re: [j-nsp] JUNOS BootP-relay Behaviour

alain.briant at bt.com wrote:
> When I configure DHCP relay like this on an EX switch:
>  
> "set forwarding-options helpers bootp interface XX server @IPDHCPserver"
>  
> The outgoing relayed paquets are received on the DHCP server with a 
> source address of the outgoing interface of the EX switch (the Net 
> IP.B address)
>  
>                                              __________
>                         _______             {          }
>               Net IP.A |       | Net IP.B  {            }
> DHCP client |----------| EX SW |----------{      NET     }--| DHCP
> server
>                        |_______|           {            }
>                                             {__________}
>  
>  
>  
> On a C router and other brands the behaviour is different and the 
> address used is the one from the incoming interface (the Net IP.A 
> address)

We see this too, but why does it matter? DHCP servers are required to inspect the "giaddr" field in the BOOTP/DHCP header, not the source of the IP packet.

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