dorkinoPremium
join:2004-02-22
Atlanta, GA | Default gateway not near me Is it normal for my default gateway to have a response time of 20-30ms? The next two hops beyond it show as being in my town (Cumming, GA - according to their DNS response), and those two hops show around 8-10ms response. The gateway has no DNS response, but if I look it up in IP DB lookup tools, it claims to be located in Conyers, GA OR Marietta, GA - both of which are about 30-45 minutes away.
This thread seems to indicate it's possible that we get stuck with less than ideal routing configurations based on the IP we get... »[Speed] Comcast changed my Gateway IP. Speed dropped dramaticall
The reason I'm posting is because I can see dropped packets when I ping the gateway with large packets (8000 bytes or larger). Sometimes I have problems getting streaming videos to start because of this. I've asked Comcast Steve to look into it, and he looked and re-provisioned my modem, but I ended up with the same IP and same issues. I also tried swapping out the old SB 6120 with a new SB 6121, but that changed nothing.
I can get it to pull a different IP on a different gateway by spoofing a MAC in the router, but that gateway behaves in a similar fashion w/ 20-30ms response time and dropped packets. It seems like 20-30ms is rather high for a 1st hop out.
Ping tests using tools on this site show no problems pinging the gateway, but if I try to ping my IP, it shows anywhere from 50-90% packet loss. Which makes me wonder just how far away is that gateway? |
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andyrossPremium,MVM
join:2003-05-04
Schaumburg, IL | How consistent are the pings to the gateway? It may be configured to give them low priority. For Windows, you can try a "ping -t www.xxx.yyy.zzz" to ping continuously. Hit Ctrl-C to stop. |
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biomeshPremium
join:2006-07-08
Tomball, TX Reviews:
 ·Comcast
| reply to dorkino
I don't know what your routing looks like, but the MTU on most ethernet networks is only 1500 bytes, so you will start to see fragmentation after that. The issues from the fragmentation could be caused by any number of network devices along the way(including your router, etc). If you have gigabit router/switches with jumbo frames enabled - try to disable it (usually on your nic and the switch/router) and try your tests again.
The dns reverse lookup tables are not always 100% accurate, btw. |
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dorkinoPremium
join:2004-02-22
Atlanta, GA | reply to dorkino
Here's a line test to my IP: »/pingtest/98cb···/2882164 |
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dorkinoPremium
join:2004-02-22
Atlanta, GA | reply to andyross
I'm using the -t switch along with -l to increase the buffer size. I've let it run for 30 minutes.
I do not have jumbo frames enabled on my switch or router. When I ping my cablemodem, I can ping it using 8000 bytes with no problem, but maybe it's unusual or a bad test to do so to the gateway. So I've tried it both with 8000 bytes and 1500 bytes:
8000:
C:\>ping (gateway ip) -t -l 8000
Pinging (gateway ip) with 8000 bytes of data:
Reply from (gateway ip): bytes=8000 time=22ms TTL=254
Reply from (gateway ip): bytes=8000 time=20ms TTL=254
Request timed out.
Reply from (gateway ip): bytes=8000 time=20ms TTL=254
Reply from (gateway ip): bytes=8000 time=21ms TTL=254
Reply from (gateway ip): bytes=8000 time=22ms TTL=254
Reply from (gateway ip): bytes=8000 time=23ms TTL=254
Reply from (gateway ip): bytes=8000 time=22ms TTL=254
Reply from (gateway ip): bytes=8000 time=23ms TTL=254
Reply from (gateway ip): bytes=8000 time=20ms TTL=254
Reply from (gateway ip): bytes=8000 time=22ms TTL=254
Reply from (gateway ip): bytes=8000 time=22ms TTL=254
Reply from (gateway ip): bytes=8000 time=20ms TTL=254
Reply from (gateway ip): bytes=8000 time=20ms TTL=254
Request timed out.
Reply from (gateway ip): bytes=8000 time=20ms TTL=254
Reply from (gateway ip): bytes=8000 time=22ms TTL=254
Request timed out.
Reply from (gateway ip): bytes=8000 time=15ms TTL=254
Reply from (gateway ip): bytes=8000 time=19ms TTL=254
Reply from (gateway ip): bytes=8000 time=21ms TTL=254
Reply from (gateway ip): bytes=8000 time=22ms TTL=254
Reply from (gateway ip): bytes=8000 time=30ms TTL=254
Reply from (gateway ip): bytes=8000 time=21ms TTL=254
Request timed out.
Reply from (gateway ip): bytes=8000 time=20ms TTL=254
Reply from (gateway ip): bytes=8000 time=21ms TTL=254
Ping statistics for (gateway ip):
Packets: Sent = 27, Received = 23, Lost = 4 (14% loss),
Approximate round trip times in milli-seconds:
Minimum = 15ms, Maximum = 30ms, Average = 21ms
Control-C
1500:
C:\>ping (gateway ip) -t -l 1500
Pinging (gateway ip) with 1500 bytes of data:
Reply from (gateway ip): bytes=1500 time=17ms TTL=254
Reply from (gateway ip): bytes=1500 time=17ms TTL=254
Reply from (gateway ip): bytes=1500 time=18ms TTL=254
Reply from (gateway ip): bytes=1500 time=16ms TTL=254
Reply from (gateway ip): bytes=1500 time=18ms TTL=254
Reply from (gateway ip): bytes=1500 time=16ms TTL=254
Reply from (gateway ip): bytes=1500 time=29ms TTL=254
Reply from (gateway ip): bytes=1500 time=18ms TTL=254
Reply from (gateway ip): bytes=1500 time=26ms TTL=254
Reply from (gateway ip): bytes=1500 time=18ms TTL=254
Reply from (gateway ip): bytes=1500 time=16ms TTL=254
Reply from (gateway ip): bytes=1500 time=17ms TTL=254
Reply from (gateway ip): bytes=1500 time=40ms TTL=254
Reply from (gateway ip): bytes=1500 time=52ms TTL=254
Reply from (gateway ip): bytes=1500 time=17ms TTL=254
Reply from (gateway ip): bytes=1500 time=15ms TTL=254
Reply from (gateway ip): bytes=1500 time=16ms TTL=254
Reply from (gateway ip): bytes=1500 time=17ms TTL=254
Reply from (gateway ip): bytes=1500 time=18ms TTL=254
Reply from (gateway ip): bytes=1500 time=16ms TTL=254
Reply from (gateway ip): bytes=1500 time=17ms TTL=254
Reply from (gateway ip): bytes=1500 time=15ms TTL=254
Reply from (gateway ip): bytes=1500 time=17ms TTL=254
Reply from (gateway ip): bytes=1500 time=18ms TTL=254
Reply from (gateway ip): bytes=1500 time=15ms TTL=254
Reply from (gateway ip): bytes=1500 time=16ms TTL=254
Reply from (gateway ip): bytes=1500 time=17ms TTL=254
Reply from (gateway ip): bytes=1500 time=15ms TTL=254
Reply from (gateway ip): bytes=1500 time=16ms TTL=254
Reply from (gateway ip): bytes=1500 time=17ms TTL=254
Reply from (gateway ip): bytes=1500 time=17ms TTL=254
Reply from (gateway ip): bytes=1500 time=15ms TTL=254
Reply from (gateway ip): bytes=1500 time=16ms TTL=254
Reply from (gateway ip): bytes=1500 time=30ms TTL=254
Reply from (gateway ip): bytes=1500 time=16ms TTL=254
Reply from (gateway ip): bytes=1500 time=16ms TTL=254
Reply from (gateway ip): bytes=1500 time=18ms TTL=254
Ping statistics for (gateway ip):
Packets: Sent = 37, Received = 37, Lost = 0 (0% loss)
Approximate round trip times in milli-seconds:
Minimum = 15ms, Maximum = 52ms, Average = 19ms
Control-C
Pinging using 1500 bytes doesn't appear to result in dropped packets, but the response time still seems to be a bit high for the first hop out. Am I just crazy in thinking that my default gateway should be closer and/or faster? Also, what's up with that pingtest? |
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 espaethDigital PlumberPremium,MVM
join:2001-04-21
Minneapolis, MN
kudos:2
 ·Clear Wireless
| said by dorkino:Am I just crazy in thinking that my default gateway should be closer and/or faster? You're making the assumption that the CMTS is replying to your ICMP echo request immediately after receiving it; that you're getting lower latency from the hop beyond it tells you that's not the case.
What you're observing is the combination of network delay plus processing delay. This isn't concerning because ICMP echo replies are part of a maintenance process that has very little relation to performance in the packet forwarding process. |
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biomeshPremium
join:2006-07-08
Tomball, TX Reviews:
·Comcast
| reply to dorkino
An 8000 byte ping is a bad test. Also, you need to know that devices can place QOS (quality of service) levels on different types of traffic - especially icmp traffic - i.e. ping. Your router could just be busy.
If youtube is your only issue, it could be something totally different than just a router. (Caching server, etc) |
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harald
join:2010-10-22
Columbus, OH
kudos:1 | reply to dorkino
Your gateway is near you, a matter of a few miles.
It can't be a town or two away. Not possible.
You are only connected to one gateway. Chaning your MAC cannot change your physical gateway. The IP address that you see as your gateway is the address of a port on your gateway, one single CMTS located near to you. |
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dorkinoPremium
join:2004-02-22
Atlanta, GA | Is it normal then to receive a completely different IP (a 174.x.x.x instead of 24.x.x.x) if I change the MAC on my router? |
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DrDrew
join:2009-01-28
Apple Valley, CA
kudos:6
1 edit | said by dorkino:Is it normal then to receive a completely different IP (a 174.x.x.x instead of 24.x.x.x) if I change the MAC on my router?
yes. There are several different subnets assigned to the CMTS your modem is connected to.
BTW, the MTU for standard ethernet and the cable modem connection is 1500 so your packets 8000 are getting broken up automatically. That's what is slowing down the responses for the large packets.
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If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes. |
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 EGThe wings of lovePremium
join:2006-11-18
Union, NJ
kudos:9 | reply to harald
said by harald:Your gateway is near you, a matter of a few miles.
It can't be a town or two away. Not possible.
Any possibility of a regional S.H.E. (Super Headend) located farther away than traditional local ones ? |
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dorkinoPremium
join:2004-02-22
Atlanta, GA | reply to dorkino
Alright, thanks everybody. I guess the only outstanding question I have is why is the ping test showing such horrible results? If I run the pingtest to another IP that is presumably behind the same gateway (I changed only the last octet), it runs fine. But to my IP it shows significant loss.
That led me to think maybe there's a problem with my particular setup, which prompted the replacement of my modem. I've tried removing the router and hooking a PC directly to the modem - same lossy pingtest result. Tried moving the cable wire to another wire in the house - same result. The cablemodem is directly off of one leg of a 2-way splitter from the cableco line. Signals are great.
I think I'm probably just misunderstanding these "test results" that I'm getting, and perhaps over-analyzing a situation that's not too broken in the first place. |
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DrDrew
join:2009-01-28
Apple Valley, CA
kudos:6 | said by dorkino:Alright, thanks everybody. I guess the only outstanding question I have is why is the ping test showing such horrible results? If I run the pingtest to another IP that is presumably behind the same gateway (I changed only the last octet), it runs fine. But to my IP it shows significant loss.
That led me to think maybe there's a problem with my particular setup, which prompted the replacement of my modem. I've tried removing the router and hooking a PC directly to the modem - same lossy pingtest result. Tried moving the cable wire to another wire in the house - same result. The cablemodem is directly off of one leg of a 2-way splitter from the cableco line. Signals are great.
I think I'm probably just misunderstanding these "test results" that I'm getting, and perhaps over-analyzing a situation that's not too broken in the first place.
It could be a home router, firewall, or other anti-malware software.
So what do you have? I doubt you have the PC directly connected to the modem with nothing protecting it.
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If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes. |
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dorkinoPremium
join:2004-02-22
Atlanta, GA | reply to dorkino
CM signal levels |
Line to Modem:
CableCo line -> 2 way splitter -> long cable run spliced together twice using "blue" barrel connectors (approx 100 feet total) run through the attic, terminating at a wiring panel in the laundry room -> SB 6121 cablemodem. (CM signals are in the attached pic)
From this point, the cablemodem and rest of the equipment is all located on a panel in the laundry room:
SB 6121 CM -> ASUS RT-N16 router -> Netgear JGS524 24-port gigabit ethernet switch (unmanaged)
I have my house wired with two drops in every room, and all those drops are terminated at a patch panel that's connected to the switch via short 3' or so patch cables. I've tested connectivity between ports using iperf and can sustain over 900Mbps transfer speeds, so the internal wiring seems good.
Now as far as the computer goes, my main PC is running ESET NOD32 AV, Malware Bytes anti malware, and the Windows firewall is on. I have tested from multiple computers - another that's basically identical to this one, and an older HTPC that's running MSE and Malware Bytes and Windows Firewall. I've also tried from a few laptops with similar configs. |
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DrDrew
join:2009-01-28
Apple Valley, CA
kudos:6 | said by dorkino:SB 6121 CM -> ASUS RT-N16 router -> Netgear JGS524 24-port gigabit ethernet switch (unmanaged)
...
Now as far as the computer goes, my main PC is running ESET NOD32 AV, Malware Bytes anti malware, and the Windows firewall is on. I have tested from multiple computers - another that's basically identical to this one, and an older HTPC that's running MSE and Malware Bytes and Windows Firewall. I've also tried from a few laptops with similar configs.
I'd guess something on your PC or router is purposely limiting pings... packet flood or DDoS protection are common options that affect ping tests
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If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes. |
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quatrixPremium
join:2005-02-11
Davie, FL
kudos:2 | reply to dorkino
said by dorkino:C:\>ping (gateway ip) -t -l 8000 The gateway IP isn't classified or sensitive information. The corresponding host name might give a general location, but you already list your city. And nobody can do anything to you specifically just by knowing the gateway. One gateway could serve thousands of cable modems. Mine is 98.249.232.1 (and can be changed in about two minutes by changing the router's MAC), big deal. |
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 IowaCowboyPremium
join:2010-10-16
Indian Orchard, MA
·Verizon Broadban..
·Comcast
·AT&T Wireless Br..
·Verizon Wireless..
| reply to EG
said by EG:said by harald:Your gateway is near you, a matter of a few miles.
It can't be a town or two away. Not possible.
Any possibility of a regional S.H.E. (Super Headend) located farther away than traditional local ones ? I am in Springfield, MA and the Comcast headend for my area is in Westfield which is 14 miles away from my location. As a matter of fact, I was able to go on a tour of that facility once. They have all kinds of fancy equipment there.
To sum it up in a few words, the headend or gateway can be a few towns over. We have a Comcast office in Springfield but the headend equipment is in Westfield. If I need to go to an office, I'll go to Westfield as there is never a line most of the time.
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All of my CPE (including my EMTA) is customer owned. The only Comcast owned equipment in my house is the CableCards in the two TiVO boxes I own. |
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 tenpin784I Went To The Dark Side?
join:2001-03-30
New Durham, NH | reply to harald
said by harald:Your gateway is near you, a matter of a few miles.
It can't be a town or two away. Not possible.
Not true. I know for a fact my gateway is 35 miles as the crow flies away from my house. How do I know this? Cause I worked for the cable company, and was their DOCSIS/CMTS engineer.
Edit: And the fiber goes through 5 towns on it's way back to the headend, and its a 45-50 minute drive.
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Dream as if you'll live forever, live as if you'll die today.
Disclaimer: These are MY comments, my employer cant be held responsible. |
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 brianmcdPremium
join:2000-09-06
Norristown, PA | reply to dorkino
I have always had my Networks (DSL/Comcast/FIOS) Configured so that the Default Gateway and one of the DNS addresses provided to all my PCs was the Router (192.168.1.1). I would also use a 2nd DNS Provider. |
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dorkinoPremium
join:2004-02-22
Atlanta, GA | said by brianmcd:I have always had my Networks (DSL/Comcast/FIOS) Configured so that the Default Gateway and one of the DNS addresses provided to all my PCs was the Router (192.168.1.1). I would also use a 2nd DNS Provider.
I'm referring to my router's gateway. |
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