Hello Tony,

you cannot have a router in two BGP ASes at the same time

You can pretend to be in another As using:

neigh xxx local-as yyy

see what happens:

RT-RM-TLD066-DMZ-C-1#sh ip prot sum

Index Process Name

0 connected

1 static

2 isis

3 bgp 8234

*** IP Routing is NSF aware ***

RT-RM-TLD066-DMZ-C-1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

RT-RM-TLD066-DMZ-C-1(config)#router bgp 5000

BGP is already running; AS is 8234

RT-RM-TLD066-DMZ-C-1(config)#^Z

RT-RM-TLD066-DMZ-C-1#sh ip prot sum

Index Process Name

0 connected

1 static

2 isis

3 bgp 8234

*** IP Routing is NSF aware ***

RT-RM-TLD066-DMZ-C-1#

hope to help

Giuseppe