Patton electronic SmartNode 4110 Series Manuel D’Utilisation

PPP configuration task list

SmartWare Software Configuration Guide 

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The PPP remote peer offers an IP address for the 
IP interface. The IP interface adopts this IP 
address

Once PPP has established an IP connection, the 
IP interface can use DHCP to acquire an IP 
address. It sends a DHCP Discover message 
(which is an IP broadcast) to the IP network to 
which PPP has established connection. If no 
DHCP Server is present, the IP interface does 
not adopt the IP address offered by the PPP 
remote peer but leaves the IP address unde-
fined.

The IP interface requests from the PPP remote 
peer to use the IP address ip-address. PPP 
repeatedly tries to set-up a connection until the 
remote peer accepts this IP address. It does not 
accept any other IP address offered by the PPP 
remote peer. The parameter netmask specifies 
the size of the subnet in case ‘no point-to-point’ 
is configured

(optional)

Limits to the MSS (Maximum Segment Size) in 
TCP SYN packets to mss or to MTU (Maximum 
Transmit Unit) - 40 Bytes, if ‘mtu’ is used. ‘rx’ 
applies to packets which arrive inbound at this 
IP interface, ‘tx’ to packets which leave out-
bound of this IP interface.

PPP over Ethernet connections impose an over-
head of 8 Bytes (PPP: 2 Bytes, PPPoE: 6 Bytes). 
Some Ethernets do not allow payloads larger 
than the 1500 Bytes which the standard 
defines, so IP packets must not contain more 
than 1492 bytes when transmitted over such 
connections. Reducing the MTU/MRU to 1492 
Bytes does not always solve the problem 
because many sources do not allow fragmenta-
tion of the IP packets they send (they set the 
‘Don’t fragment’). However, these sources limit 
the size of the IP packets according to the MSS 
which their peers announce in the TCP SYN 
packets.

It is recommended to use ‘mtu’ inbound and 
outbound.