Black Box LR1114A-T1/E1 Secondary Addressing 29 Bit, Routing Considerations for IP Multiplexing

IP Multiplexing

6.1.8 Secondary Addressing – 29 Bit

This approach utilizes a 29-bit subnet for each remote connection. Within each 29-bit subnet is the POP router secondary, the Black Box WAN addressing, and the remote router secondary.

POP Router	e0:	200.1.1.1/30 primary
		199.1.1.1/29 secondary
		199.1.1.9/29 secondary
		199.1.1.17/29 secondary
POP Black Box	e0:	200.1.1.2/30
	wan1:	199.1.1.2/29
	wan2:	199.1.1.10/29
	wan3:	199.1.1.18/29
Black Box 1	e0:	201.1.1.2/30
	wan	199.1.1.3/29
Router 1	e0:	201.1.1.1/30 primary
		199.1.1.4/29 secondary
Black Box 2	e0:	202.1.1.2/30
	wan1:	199.1.1.11/29
Router 2	e0:	202.1.1.1/30 primary
		199.1.1.12/29 secondary
Router/DSU	s0:	199.1.1.19/29

6.1.9 Pros and Cons of Different IP Addressing Schemes

The following table provides information about addressing scheme pros and cons.

Table 10 Addressing Schemes: Pros and Cons

Approach	Pros	Cons
Single Subnet	Minimizes consumption of IP	POP Black Box requires two route statements
	address space	per remote connection.
Split Subnet	Less routes required in Black	Consumes 29-bit subnet per remote site.
	Box
Secondary Addressing	Easily Scalable	Consumes 29-or 30-bit subnet per remote. Not
		transparent to certain routing protocols.

6.1.10 Routing Considerations for IP Multiplexing

„RIP / RIP2 / IGRP –Turn off split horizons to enable routing updates through secondary addresses, if used.

„EIGRP – Updates are sourced only from primary addresses, although routers will listen to updates arriving on primary and secondary.

„OSPF – For Cisco and other routers, routing updates are sourced and detected only on primary addresses, therefore secondary addressing schemes are not usable.

„BGP4 – Routing updates are fully functional over primary and secondary addresses.

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