No internet access with Static LAN IP

This morning when I got to work a couple of machines could not access the internet, including my own. The only common thing is that they have all got static IP addresses for RDC connections.

main subnet => 192.168.16.1/21
DHCP scope => 192.168.18.10 - 192.168.18.255

my static IP => 192.168.19.3

On the PC's which have a static address if i change them to DHCP everything works. If they are static they are not able to access anything external. Internal Sites work fine. DNS lookups work fine for both internal and external sites.

I have tried getting a dhcp address on my PC, then setting the exact same IP address manually and see the same restrictive behaviour. Everything was fine yesterday evening when we left, nothing has been changed. i cant see any updates have occurred. i have checked router settings and rebooted several times. still no joy.

Any Help would be appreciated.

Thanks

Michael
motorhogAsked:
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masnrockCommented:
Did you try using tracert? At least you'll know at what hop things appear to stop.
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masnrockCommented:
And you're saying nothing changed? Have you tried doing either a packet capture or traceroute? I'd try the traceroute from the systems with static IP addresses first and see what happens. Also try adding from addresses from 192.168.19.x into a DHCP scope, and see if things work normally with those.
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QlemoBatchelor, Developer and EE Topic AdvisorCommented:
Sounds as if the default gateway has changed. Did you check the one you get with DHCP versus the one you've set up manually?
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motorhogAuthor Commented:
Yeah nothing has changed. I went home yesterday evening everything was fine. Cam in this morning no internet on mine, the MD's, and a few senior managers PC's.  All have static IP addresses.

The Default Gateway address is fine in both DHCP and static settings.
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masnrockCommented:
What happens if you do a traceroute from one of the systems with a static IP? Or if you do a nslookup?
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motorhogAuthor Commented:
If i try and browse to an external IP address (to rule out a DNS issue) that doesnt work either. I am using a Draytek 3900 V router on a BT net line.
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motorhogAuthor Commented:
NSlookup works fine for both internal and external web addresses.

Tracert hops to the router but then times out for everything else.

The router is not my DHCP server either, that is my domain controller. Im not sure how the router would be able to tell the difference between a static or DHCP assigned IP
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William MillerInventory/IT ConsultantCommented:
What OS are you running on the machines in question? Also, when you say a DNS query to an external site still works does this mean when you run the nslookup command you return a valid result? For instance:

"nslookup www.google.com" should return something like:

nslookup www.google.com
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

Non-authoritative answer:
Name:    www.google.com
Addresses:  2607:f8b0:4002:811::2004
          172.217.12.68
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TjnoNetwork AdministratorCommented:
main subnet => 192.168.16.1/21
DHCP scope => 192.168.18.10 - 192.168.18.255

my static IP => 192.168.19.3

On the PC's which have a static address if i change them to DHCP everything works. If they are static they are not able to access anything external.

Open in new window


Was the static network NATed to the Internet?

Can you show the results of these commands when PCs in DHCP and static mode?
nslookup www.google.com
ping 8.8.8.8
tracert -d google.com
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masnrockCommented:
I'm assuming you can ping the Draytek from the machines with static address, so you need to be sure of what the Draytek is doing.
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motorhogAuthor Commented:
so it appears the problem was some missing IP aliases from the WAN setup on the Draytek.

Each static internal IP has a corresponding External address. Not sur ehow but some of the External Alias addresses dissapeared and so the Draytek was blocking them.

Added Aliases back in and everything seems fine for now.

Thanks
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Brian BEE Topic Advisor, Independant Technology ProfessionalCommented:
Not related to the question exactly, but it may help future problems.

Use DHCP reservations instead of static IP
Use different ports on your external address for remote desktop connections. Then you don't have to use a different external IP for each RDS connection.
Feel free to ask as a separate question if you want clarification on that.
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masnrockCommented:
How many people have access to the Draytek, how complex is the password, and what are the access mechanisms like (i.e. remote administration being allowed)? May want to check into that. If you're lucky, logs will provide some data on that.
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atlas_shudderedSr. Network EngineerCommented:
Try the simple things first.  Disconnect your PC or shut it down.  Go to a PC that is working and attempt to ping your PC's IP.  If it is still active, you have conflicts on your LAN.
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motorhogAuthor Commented:
Thanks @masnrock.

i am th eonly person who has the access details for the Draytek. The password is a 14 charachter alpha-numeric with symbols. completly Random code. i know it, dont have it written down anywhere .

I will check the logs though. All is working fine now since i put the Aliases back.
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QlemoBatchelor, Developer and EE Topic AdvisorCommented:
I've no clue why you chose masnrock's comments as answers. As every other suggestion here there was just guessing, and noone of us can have known what caused your issue (neither did any comment help in finding the culprit).
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