[Click] HELP:about make-ip-conf.pl

[Eddie Kohler]

吴保川 wrote:
> hi everyone,
> Now I am learning the configuration generated by make-ip-conf.pl. I have some questions.
> 
> 
> First,
> why the ip router does not send ARP queries? 

It does.

> why the IP router just receive ARP queries and responses ?
> 
> Second,
> what does the following mean? 
> rt[0] -> EtherEncap(0x0800, 1:1:1:1:1:1, 2:2:2:2:2:2) -> toh; 
> who is 1:1:1:1:1:1, who is  2:2:2:2:2:2 ? 

These are garbage Ethernet addresses just used as placeholders.

> Does the element toh send the frames it received to the machine with MAC address 2:2:2:2:2:2? 

Yep.

> 
> Third,
> why FixIPSrc exists ?  
> to my knowledge, if an IP packet is not used for source routing, there is no need for the router to modify the IP packet's source address. 
> But in the configuration generated by make-ip-conf.pl, the IP address of every packet which need to be forwarded is modified, for the element FixIPSrc(18.26.4.92) and FixIPSrc(1.0.0.1).

ICMP errors generated by the router use this element, since an ICMP error is 
expected to have the source address equal to the address of the interface on 
which the error is first sent.  All other types of packet (including ICMP 
errors that the router is merely forwarding) go through FixIPSrc unchanged.

Eddie


> 
> Thank you!
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