[j-nsp] source address selection for RE generated traffic addresses to direct neighbors

[Ivan Malyarchuk]

Look at default-address-selection option description:
https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/junos-software-system-management-source-address-local-tcp-ip-packets-configuring.html
For IPv4: If this option is not enabled, and destination is directly 
connected then Is-Preffered address from this subnet is used, if not 
direct then junos uses Is-Primary address of interface.

If option is enabled, then address with "Is-Default" flag used for all 
connections except some special cases like ebgp or ldp (it is lo0.0 in 
most cases)

For IPv6 there is "scope" algorithm described in rfc6724, but I am not 
sure how junos follows it.

22.01.2019 19:18, Martin T пишет:
> Hi,
> 
> how does Junos choose the source address for RE generated traffic
> addresses to direct neighbors if the application(for example ping
> utility) does not bind to specific address? Does it choose the first
> address configured on the egress interface which falls in the same
> network as the destination address? Looks like it because if I have a
> following configuration:
> 
> root at vmx1> show configuration interfaces ge-0/0/0.0 family inet
> address 10.10.1.0/31;
> address 10.10.99.100/24;
> address 10.10.99.2/24;
> address 10.10.99.3/24;
> 
> root at vmx1> show interfaces ge-0/0/0.0 terse
> Interface               Admin Link Proto    Local                 Remote
> ge-0/0/0.0              up    up   inet     10.10.1.0/31
>                                              10.10.99.2/24
>                                              10.10.99.3/24
>                                              10.10.99.100/24
>                                     multiservice
> 
> root at vmx1>
> 
> ..and I execute the "ping 10.10.99.200", then the source address is 10.10.99.2.
> 
> And for IPv6 it should be very straightforward. RFC6724 defines the
> "Prefer appropriate scope" rule and as Junos seems to allow only
> single link-local IPv6 address per IFL, then for locally generated
> IPv6 traffic addressed to direct neighbors uses that link-local IPv6
> address as a source address?
> 
> 
> thanks,
> Martin
> _______________________________________________
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> 

-- 
С уважением,
Иван Малярчук
"ИНТЕР-ТЕЛЕКОМ" Цифра
Украина, Киев
(044) 206-77-33 доб.155
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