Hi Jason,
The loss upon restoration could easily be due to microloop. Which is
caused by different convergence speed of neighboring.
When you leave only one type of routers they converge at the same speed
so no microloops.
On 13-Dec-18 02:47, Jason Lixfeld wrote:
Hi all,
I’ve been playing around with rLFA in a small lab using a pair each of
MX204-IR, ASR920, ME3600s in a ring:
MX1-et0/0-MX2-xe0/1-ASR2-ge-ME2-ge-ME1-ge-ASR1-te-MX1
They're all running BFD (150ms x 3), LDP, ISIS, LDP-IGP sync (infinite
holddown), LDP session protection and LDP GR (not that GR really applies here,
but…)
MX1, MX2, ASR1 and ASR2 have a single armed host hanging off each of them. The
test consists of H-ASR1 pings to H-MX2, and H-ASR2 pings to H-MX1. In both
cases, it’s sudo ping -fi 0.001 ${host}
ASR1 has rLFA for H-MX2 subnet, ASR2 has rLFA for H-MX1 subnet, MX1 has rLFA
for H-ASR2 subnet, and MX2 has rLFA for H-ASR1 subnet.
With this topology, when I pull the plug between MX1 and MX2, I lose a ping or
two, but when I connect MX1 and MX2 again, there’s about 500ms of loss on all
tests.
If I re-jig the topology and move the MX1-MX2 link from et0/0 to also be
xe-0/1, the failover and tailback both lose about 500ms worth of traffic.
If I re-jig the topology and remove the MX1-MX2 links entirely and instead
create a link between ASR1 and ASR2 to close the ring, there’s zero loss on the
failover of that ASR1-ASR2 link, and only about 10ms loss on the fail back.
This is all really surprising to me. Surprising that when the MX1-MX2 link is
on et0/0 it behaves one way, and another way when the MX1-MX2 link is on xe0/1
(PIC0 vs PIC1). Also, surprising that it didn’t seem to perform as well as
when the ASRs were closing the ring instead of the MXs.
I really thought this testing would be much more uneventful than it has been.
If I think through this as rationally as I understand it, the only thing that
seems to make sense is that on the MX, the FIB is a bit out of sync with the
RIB, worse based on the PIC.
I’m pretty new to JunOS and Juniper HW architecture in general, so there’s no
doubt much that I don’t know.
Thoughts?
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