Can someone give this network IP setup a once over for me?

dbwillis

dbwillis

[H]F Junkie
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Jul 9, 2002
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Customer called me after replacing his DSL modem..."we cant get online"

OK, let me see, I cant get in, did ATT help you configure your new DSL/Router?
- NO!

I walked him through it by memory, but the internet access seems to be slow since the new modem/router was installed.

Old was a 2Wire basic with wifi (1000 something model, very old)
new one is a Netgear 7550 something (he bought it at the ATT store)

DSL/public side is DHCP and gets a good IP.
Private side is set to 172.16.1.1, 255.255.0.0 (no DHCP)
Server is set to 172.16.1.5, 255.255.0.0
Servers DNS (AD) is set to use 8.8.8.8 and 8.8.4.4 as forwarders
DHCP (via Server) is set to 172.16.1.100 to 125, 255.255.0.0, 172.16.1.1 as gateway, 172.16.1.5 as dns

Only thing that has changed is the DSL modem/router and now internet access seems slow.
I did the speedtest (speedtest.espn.com) and the results matched what I had screenshot back in Feb

Should the subnet be 255.255.255.0 instead?
All flat network of 15 computers and 2 printers, no wifi, all gig connections
 
255.255.0.0 is a perfectly valid subnet. It's a bit more extra space than you might need for a network that size, but it shouldn't be a problem. Can you ping the gateway from the client? Is DNS set up properly on the client?
 
No that subnet is correct. It's a class B network.

Has he contacted the ISP?

What's the issue? It's slow or he can't get online? I'm confused by your post. Try renewing his DHCP lease.
 
Hes just reporting its slow, he reports it to me since ATT starts asking him all sorts of questions that he doesnt know, but Im at work (day job)
I can ping the gateway (172.16.1.1) from all clients and server
Clients use the AD server as DNS, server has AD DNS (forward/reverse zones) correct and can resolve internet names quickly and without error, the DNS gui also resolves the forwarders quickly (8.8.8.8 and 8.8.4.4)
I wasnt sure if the 255.255.0.0 would be a problem, I normally always use 255.255.255.0, but I think used 255.255.0.0 because the old dsl modem/router was coded to that and I couldnt set 255.255.255.0

I can release/renew the DSL IP address through the modems config page, no problems there (had thought maybe his username/pass was wrong and it was trying to redirect to ATT web sites, but found that was the ATT software they had him install when he initially called)
I havent gotten there yet, he closes at 5 and I get out at 5 and am ~20 min away
 
Nope, DSL mdem/router is set to not give DHCP on the private (internal) side
 
I had someone complain that their connection was so slow they couldn't do anything. I went to check it out and found they had a filter on the line going into the DSL modem.
 
Thats a good thing Ill check, they did some moving around of the fax machine, but that was ~2 months ago
 
And it was recently that they swapped out the modem. Neophytes do crazy things in attempts to solve issues themselves... I can't tell you how many times I have found the Cable modem plugged into the LAN side of the router.
 
Hah, that was my aunt Sunday night after she replaced the Netgear wifi router with a Belkin because the uncles Nook would drop wifi.
"I even plugged the old one back in but still cant get online"
 
Solved -
Paint area had spilled some acetone on a bench, which wiring from before my time, ran behind, said acetone had dripped on the cable, melting the covering off the Cat5 cable
 
And that ladies and gents, might be the damn craziest reason I've seen for slow internet in awhile.

You win cake
 
That's crazy. And a great reminder that we can't assume anything cause you'll always run into the WTF-factor. :D
 
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