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New Member

RV320 MTU Wrong

I have a PPPoE connection that has an MTU of 1492.  Every router I have ever used passed this size packet.  The RV320 is passing a MTU packet of 1440.  Can someone verify and perhaps have a solution?  I wouldn't think that Cisco programmed it this way.  I have turned off everything I can find that isn't needed.

As a test, I connected a Cisco ISA550 to the modem and it gave me the proper MTU.  So I know it's right but how do I get the RV320 to perform?

Thanks

15 REPLIES
Gold

RV320 MTU Wrong

DNS Admin,

Go to Setup-> Network and edit the WAN connection. You should be able to configure the MTU value after changing it to manual.

- Marty

New Member

RV320 MTU Wrong

Thanks for your reply.  I'm sorry I wasn't clear but i have done that several times and it makes no difference.  The firmware needs to be tweaked.  It will not allow a number higher than 1500 and that gives me a 1440 MTU when I test it.

I hate to waste time holding on the phone so if someone knows if this has been reported, please let me know.

New Member

RV320 MTU Wrong

OK this is interesting.  I just connected to the RV320 using VPN and am getting the same MTU 1440.  This is strange . There is an issue with the firmware in this device.

Gold

RV320 MTU Wrong

DNS Admin,

I checked the firmware release notes and found no issues listed with MTU. I also searched for a previous case and found nothing.

If your router is on the latest firmware you might test it with factory default settings (back up your config first). If the issue persists, call or start a chat session and get a case open: www.cisco.com/go/sbsc

What are you using to check the MTU?

- Marty

New Member

Re: RV320 MTU Wrong

I pulled the RV320 out of service and reloaded the latest firmware, reset to factory defaults, and connected to my ISP.  The MTU is set at "AUTO" although I tried to set it manually and it will not accept a number higher than 1500.  The TCP tools at speedguide.net are reporting a MTU of 1440 and a MSS of 1400.  The connection is PPPoE so it should be 1492 and 1452 respectively. 

If I remove the RV320 and connect the ISA550 it reports 1492 and 1452 as does any other router - EXCEPT for 1 particular router.  In my testing I connected a RV042G to the connection and got the same MTU that the RV320 is reporting.  Perhaps no one pays attention to this so it has not been reported.  It seems strange that the predecessor to the RV320 (RV042G) has the same issue. 

As a side note - all computers on the network are Macs.  I even checked the MTU with a *nix terminal command.  If i connect just my computer to the ISP, I also get the standard MTU.

New Member

Re: RV320 MTU Wrong

I have the same issue.  I found that if I disable the firewall, the issue disappears.  There is a restrictive slow down in the firewall on the RV320.  If I disable it, I get the 1492 MTU which is standard on a PPPoE WAN type.  Of course you need the firewall so when I enable it, the MTU drops to 1440 on a DSL (PPPoE) network.

I don't know if any engineers for Cisco browse these forums, but that is something that ought to be looked at.

Bronze

Re: RV320 MTU Wrong

Quite strange.  Besides the wrong MTU, is there any other noticable speed difference?  If not, then it may not be a big enough thing to worry about.

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New Member

Re: RV320 MTU Wrong

Yes there are other issues.  I have a persistent packet loss of about 4%.  When the firewall is off, there is no packet loss.  It is a big deal and needs to be addressed.  It is extremely annoying when you are trying to tune a network tcp parameters and have a reproducible defect with equipment and the response is "well it's no big deal".  Depending on the size of the network, little things add up to BIG things!

Bronze

Re: RV320 MTU Wrong

Well, welcome to smb routers and the lack of immediate support. You've discovered a bug, which is great, but the chances of getting it fixed in less than a month is very unlikely.  It's just the nature of smb routers in general.

You're left to deal with this on your own and find your own workaround until the bug is actually fixed.  I personally know exactly how frustrating this is, but unless you're willing to spend the big dollars to jump into enterprise-class routers, this will be your quickest path to a working resolution.  Demanding a solution won't help, and even switching brands may not solve the issue (although in your case I could see it solving this issue).  Downgrading the firmware will likely be a good solution, as it probably wasn't broken in a previous version. 

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Gold

Re: RV320 MTU Wrong

John,

While Cisco engineers read and reply in these forums, this is not the place to report a bug. This is a place to get some troubleshooting ideas and maybe get your issue resolved without having to contact support.

It doesn't appear that anyone else has any new ideas regarding how to fix this issue. If you are experiencing this issue, please call or start a chat session and get a case open:

www.cisco.com/go/sbsc

If the issue cannot be resolved at Level 1, your case will be escalated. Note that support will likely want to gather information such as the config file from the router, topology and packet captures. If it is confirmed that this is in fact a bug, the development team will be notified and they will start working on a resolution for a future firmware release.

If you do not open a case the development team will never know that you are having the issue and therefore will not try to fix it. Also, the more cases that come in for the same issue, the higher priority the issue becomes. Everyone experiencing the same problem should open a case.

- Marty

New Member

RV320 MTU Wrong

Well I have verified that the MTU issue is in the firewall.  I have disabled everything that I don't need in the router and still getting an MTU of 1440.  I disable the firewall and immediately the MTU went to 1492 (normal for PPPoE)

I suppose I will chat support to see if I can get this fixed. 

New Member

Re: RV320 MTU Wrong

Well that did NO good at all!!!!!  I contacted tech support and they more or less blew me off.  Their response is that it's good enough.  I sent the test results clearly showing the issue but he didn't really see a problem with it.

I think I am SO done with Cisco!!!  I have purchased a ton of their routers/switches/security devices over the years but lately everything in the small business market is half-baked!

You are correct Samir!!  I should have just listed to you and returned the item immediately.

Gold

Re: RV320 MTU Wrong

John,

What is your case number?

- Marty

New Member

Re: RV320 MTU Wrong

629413225

Thanks for your interest.  I was told by the tech - in India no less - that it wasn't a problem.  There is a definite difference in the responsiveness of the network when the MTU is set lower than it should be.  If this issue could be corrected I would be willing to continue on since I know Cisco better than any other.

Thanks Marty

Bronze

It's not just Cisco that's

It's not just Cisco that's half-baked in the small business market--the whole market has turned into this.  I've dealt with the same type of support issues from all the major players.  It's just the nature of the game.  A 90% product is 'good enough'.

That being said, the smb products provide a huge bang for the buck when working in your infrastructure.  I'm able to do things for pennies on the dollar compared to 10 years ago.

It's a give and take.  The clear choice is that if something doesn't work, you just change it and get the job done.  Brand loyalty isn't what it was in decades past.
 

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