Juniper MX Sizing

I am wondering if anyone can provide their real world experience about sizing Juniper MX routers as it relates to BGP. I am needing a device that has a mix of layer 2 and 3 features, including MPLS, that will have a very low port count requirement that will primarily be used at a remote POP site to connect to the local IX as well as one or two full route transit providers. The MX104 has what I need from a physical standpoint and a data plane standpoint, as well as power consumption figures. My only concern is whether the REs have enough horsepower to churn through the convergence calculations at a rate that operators in this situation would find acceptable. I realize that 'acceptable' is a moving target so I would happily accept feedback from people using them as to how long it takes and their happiness with the product.

For those of you that deem the MX104 unacceptable in this kind of role and moved up to the MX240, what RE did you elect to use?

Graham Johnston
Network Planner
Westman Communications Group
P think green; don't print this email.


We use both the MX240 and MX480 (for 100G) 1800REs. Very happy with this hardware.

Jason Bothe, Manager of Networking

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If you are looking for small foot print I +1 the 240s.

Is your sizing concern just for the RIB, or also for FIB to sync up? The latter was a problem for us, but not the former. We also have inline-jflow turned on and that is still a work-in-progress in terms of impacting performance.

We are using MX104 for similar purposes for many months now, and with some tweaks in our procedures and configurations we found it to be acceptable. MX104 may not be able to process routes as fast as MX480, but MX480 is also not instantaneous either so similar risks exist.

If you're looking at scaling passed the mx104, I would consider the mx480
chassis. The price delta between the 240 vs. 480 bare chassis is negligible
and you'll get more slots to grow into. Especially, if you have a need to
do sampling or anything else that may require a service pic.


It's more about FIB than RIB as I am concerned about the time it takes until MPCs have updated route information after large scale changes in routes learned via BGP.

Graham Johnston
Network Planner
Westman Communications Group
think green; don't print this email.

Then you should look for something other then the MX104.

In our testing an MX104 running Junos 13.3R4 with a single, full feed took about 4min 25sec to (1) converge the RIB from a router sitting 0.5ms RTT away and (2) update the FIB with all entries. This performance was observed with single RE and dual RE and without any excess services running. If we added inline-flow sampling to the device full convergence took closer to 5min 45sec in our lab. Efforts to bring the convergence time down (without filtering ingress advertisements) with the assistance of JTAC proved unsuccessful.

We decided to “bite the bullet” and procure MX480s instead but obviously that’s not possible for everyone. If the MX480 is out of the question a Brocade CER Premium is an option. We have 3 in production and see very attractive convergence times; however, they have a more limited feature set and you’ll want to understand how their FIB memory scales. Apologies, I don’t know the Cisco equivalent from the ASR line these days but I’m sure others on the list could help out.

What’s a cheaper alternative to the MX104s?

We take a full BGP table and are on the AMS-IX and DE-CIX and are looking for a new router. The MX series looks a bit out of budget but we’re currently looking into the Brocade MLX series. We push under 10Gbps, but we do need 10Gbps routing due to capacity issues during attacks.

Sorry for being a bit off-topic here.


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MX480 is also not instantaneous, so the same problem applies. Brad, do you have the number for MX480 for comparison?

What we decided was, given both models suffer the same problems, just different duration, we decided to mitigate the problem and not spending the money.


We haven’t received the MX480 gear yet (POs just went in about a week ago). But we tested MX960s with the same RE-S-1800x4 w/ 16GB RAM RIB+FIB convergence time was roughly 45sec. We never worried about getting a super accurate time for the MX960 because even an “eye test” showed it was fast enough for our application and we were much more concerned with other parts of the box. Also, we had inline-flow reporting configured on the MX960. Actually, the MX960’s had a full, production-ready config while the MX104 was tested with a stripped down after we discovered the slow convergence.

Once we get some MX480s on the bench I’ll report back.

We have both Brocade CER and XMR (predecessor to the MLXe) in our environment today. We find both platforms attractive from a price and power consumption standpoint. They will both handle the IPv4 and IPv6 unicast routing tables today.* The MLXe with MR2 cards is quite a formidable box; lots of power and pretty light-weight OS (compared to Junos). We found our XMR nodes with original mgmt cards and Gen1 line cards converge pretty quick; we’ve never timed one officially but my gut feeling is RIB+FIB convergence is roughly 45sec assuming your peer is RTT nearby. The CER is a little slower to converge in our experience; however, we have them in non-critical portions of the network so I can’t really attest to their convergence performance. Sorry.. not much in the way of lab readings for our Brocade gear.


Running MLXe with MR2 and/or CER-RT as MPLS PEs depending on POP size. We also run the later as route reflectors.

They behave beautifully when it comes to churning BGP full feeds, convergence is around 30-45s (full RAM). Routing capacity is also amazing.

I'm particularly amazed by the CER-RT from a price/performance/footprint perspective. So I would advice it unless the OP has some specific technical requirements (flowspec support, etc.).

Best regards.


Did you ever get the numbers for the MX480?

I would not expect a difference in performance for the MX480 vis a vis
the MX960 using the same RE's, MPC's and SCB's.



You are right that makes sense. So as a recap, you were seeing about 45
seconds route convergence time using RE-S-1800x4 w/ 16GB RAM. For a MX104
it took 4min 25sec. I assume a MX80 would be even slower than an MX104.

What about a MX480 with RE-2000's with 4GB of ram? Does anyone have any
stats on that? I would assume faster than a MX104 but slower than the
w/ 16GB RAM.

I don't have empirical data, but yes, the MX80 and MX104 will be way
slower across the board.