description ppp with asymmetric multilink

addrouter r1
int ser1 ser - $1a$ $1b$
!
vrf def v1
 rd 1:1
 exit
int ser1
 enc ppp
 ppp ip4cp close
 ppp ip6cp close
 vrf for v1
 ipv4 addr 1.1.1.1 255.255.255.0
 ipv6 addr 1234::1 ffff::
 exit
!

addrouter r2
int ser1 ser - $1b$ $1a$
!
vrf def v1
 rd 1:1
 exit
int ser1
 enc ppp
 ppp ip4cp close
 ppp ip6cp close
 ppp multi 1500 long
 ppp frag 256
 vrf for v1
 ipv4 addr 1.1.1.2 255.255.255.0
 ipv6 addr 1234::2 ffff::
 exit
!

r1 tping 100 15 1.1.1.2 vrf v1 siz 1111
r2 tping 100 15 1.1.1.1 vrf v1 siz 1111
r1 tping 100 15 1234::2 vrf v1 siz 1111
r2 tping 100 15 1234::1 vrf v1 siz 1111