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1500 questions
28
votes
7 answers
Why can I traceroute to this IP address, but not ping?
I have an IP address and can traceroute to it, but I can not ping.
You see, I can traceroute 43.24.226.50:
dele-MBP:~ ll$ traceroute 43.24.226.50
traceroute to 43.24.226.50 (43.24.226.50), 64 hops max, 52 byte packets
1 router.asus.com…
244boy
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28
votes
8 answers
What does the 1000M on a network switch mean?
I thought the 1000M ment that it was capable of Gigabit speed but it isn't, I noticed then that it stated 10/100Mbps. What does this 1000M mean?
Jeroentetje3
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28
votes
1 answer
What are the benefits and cons of IGMP snooping?
Our new router is asking if we want IGMP snooping enabled. Not being familiar with this, I looked to the internet and got the following wiki description:
IGMP snooping is the process of listening to Internet Group Management Protocol (IGMP) network…
HorusKol
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27
votes
3 answers
Will IPv6 make private IP addresses become obsolete?
Will it still be useful to make use of private IP addresses with IPv6?
Mit94
- 373
- 3
- 5
27
votes
4 answers
How can I capture traffic on Cisco IOS switches?
For investigating a problem in client to server communication, I need to capture packets for analysis. However it's not allowed to install a packet analyzer, such as Wireshark or tcpdump, on client or server. They client is connected to a Catalyst…
Stefan
- 3,374
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27
votes
7 answers
Does it make sense to deploy OSPF across Metro Ethernet?
When I need to connect a number of branch sites to one another for a customer, I typically recommend an MPLS VPN through a trusted carrier. The CE at each site speaks BGP with its upstream PE and each site is numbered with its own private ASN. This…
Jeremy Stretch
- 4,718
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26
votes
6 answers
Is it safe to use any wifi channel in the 2.4GHz band?
It seems that everything I read about wifi says there are only three usable channels in the 2.4 GHz band; however, there are eleven 2.4Ghz wifi channels allowed in the US.
If everyone is using 1, 6 or 11, wouldn’t it make sense to use an unused…
Ron Trunk
- 66,852
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- 65
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26
votes
9 answers
Why can't devices on different VLANs, but on the same subnet, communicate?
I have a question about switching. I have two devices connected to a switch with IP addresses 192.168.5.20 and 192.168.5.10. Both devices have the same prefix, /24. That means they are on the same subnet.
If I split these devices on different VLANs…
Jim Pap
- 409
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26
votes
5 answers
Why is 4096 the max value for VLANs
The Tag Protocol Identifier is set to 16 bits.
In the CCNA certification it is said that it's not possible to have more than 4096 VLANs.
4096 in binary is 1000000000000000.
Since 16 bits are allocated anyway, the limit could be…
maxxxou
- 363
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- 4
26
votes
2 answers
Difference between unresponsive (*) and unreachable (!H) hosts in traceroute output
When running traceroutes some hops return * which as far as I know means that the host is not responding to ICMP echo request, and some other hops (mainly the last) return !H which according to the man pages it means that the host is unreachable.…
Vasilis
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26
votes
2 answers
Difference between sniffer tools
I am unsure what the following networking tools do. They all seem to do a similar thing.
First some background. I am familiar with cisco IOS. I am doing some linux networking experimentation with virtual machines so I am trying to create a small…
s5s
- 363
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25
votes
4 answers
Why must all areas connect to an Area 0 backbone in OSPF?
This question is a literal repost of the same question asked on The Cisco Support Community. Answers are unique to Stack Exchange.
Why is area 0 the backbone area in OSPF? Why must all other areas connect to it?
I have been searching for the…
Trojan
- 1,398
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25
votes
10 answers
How to find the port a device is connected to, based on IP, on a Cisco Catalyst switch
On a Cisco Catalyst switch, I need to find what port an end device is connected to.
I have the IP address/host name.
How do I quickly find the port?
Brett Lykins
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25
votes
4 answers
Does physical distance affect download speed?
I just had an argument with a colleague of mine and thought I'd just reach out to the experts on this. Here's the scenario. We were using a website that measures your connection's speed. We tested using a server that is far from us (We are in…
Navid
- 351
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- 3
25
votes
1 answer
Should IPv4 ICMP from untrusted interfaces be blocked?
Searching around I haven't been able to determine the best practice for ICMP on a firewall.
For example on a Cisco ASA would it be safe and recommended to allow ICMP from any if ICMP inspection is enabled. This would then allow for things like type…
Adam
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- 5