Does an eNodeB use same IP address for all the interfaces ?

Question

An eNodeB in LTE has many interfaces like M2, X2, S1-C , S1-U . What could be the possible deployment case ? Will all interfaces use same IP address as transport or different IP addresses for each interface ?

Answer 1

As each interface has different transport protocol
S1-C -> SCTP , X2-C - SCTP , S1-U - UDP, X2-U -UDP , M2 interface (Dont have much idea) so we may use same ip or different ip also thats why in messages where enb Share their X2-Tunnel info (transport layer address ) in ENBConfigurationTransfer message over s1 interface to get the X2 Tunnel info of other ENB through MME.

ENb can use same/different ip information for x2,s1,m2 but have to use standard port number for s1-U - 36412 and x2-u 36422.

Lets wait for experts answer ...

Answer 2

These are logical interfaces so technically all interfaces can have same Ethernet or IP Address.

However in practical box design it lot depends on the design constraint and system requirement. Since cabling in eNodeB is critical requirement and pain point so its advisable to minimize the cabling requirement so most likely to have single IP (but not a always case).

Comments

As they can have different ip used for each interface so while acquiring neighbour eNB x2 tunnel info , source eNB takes help of MME and MME get its x2 tunnel info by asking to neighbor eNB though neighbor eNB general ip info already available at MME during s1-set up.

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I hope I got your point correctly, In genral two nodes in the real field are distant a part and connected via mobile backhaul (say routers), so ideally one IP/Ethernet should not create a problem(also enodeB does not have a very high load as the case of SGW/MME). So both configurations are possible multi IP and single IP based on field requirement.