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1500 questions
10
votes
2 answers
omnidirectional antennas and the dipole antenna
This article on Cisco's website is the clearest explantion of omnidirectional antennas I've found.
What isn't so clear to me is...
1) Why is the dipole antenna the most common design for omnidirectional antennas?
2) For example, why not have an…
T. Webster
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10
votes
1 answer
How would one route an IP network through different ISPs?
So, if I have a site that has 2 (or more) internet connections, with a routable IP subnet that I own, and one ISP goes down, how do I tell the rest of the world to send traffic addressed to my network through ISP B instead of ISP A? This is in…
MDMoore313
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10
votes
1 answer
Dynamic Crypto Map with IPv6 access list
I am trying to configure a dynamic crypto map for use on a pure IPv6 network, on Cisco 15.2M. The problem is when I try to add an ipv6 access list to the dynamic crypto map, I get an error message. Below the config
crypto dynamic-map DYNMAP 5
set…
Pedro Perez
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10
votes
1 answer
Unicast RPF On the Edge
Unicast RPF is supposed to prevent source addresses that differ from what they should be to be allowed. While reading Cisco's documentation for URPF, I noticed that there are options to allow it to be used on an uplink interface by letting it go by…
coxley
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10
votes
3 answers
what to know about DSSS vs OFDM
In all the detail on DSSS and OFDM, I have missed which characterics of DSSS and OFDM make these distinct technologies. Nothing I've read appears to contrast the two.
As I understand it, both DSSS and OFDM are intended to send many bits in…
T. Webster
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- 7
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10
votes
5 answers
Packet sizes in a TCP stream
I'm network traffic and wish to divide each TCP session into a series of requests and responses (the protocols I'm working with all work that way, like HTTP or SSL).
I had a simple assumption (ignoring out of order and resent packets) - given a…
Vadim
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10
votes
8 answers
I'm setting up a Cisco CCNA lab, what equipment would you recommend?
Is it okay to use a Cisco 2948 for CCNA students, after all it's cheaper to get these switches and they have more features? Wouldn't this be better than a 2950 switch?
Lucas Kauffman
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10
votes
3 answers
What is the difference between layer-2 and layer-3 broadcasts? Please explain with an example
What is the difference between broadcast addresses ff.ff.ff.ff.ff.ff (Layer 2) and 255.255.255.255 (Layer 3)?
Rakesh Nittur
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10
votes
3 answers
3 subnets, 2 OSPF areas - Will This Work?
Will any issues occur if I have a topology involving 3 subnets and two OSPF areas where one subnet is in AREA 0 and the other two subnets are both in AREA 1?
For example:
[area 1, subnet 1]---[ABR #1]---[area 0, subnet 2]---[ABR #2]---[area 1,…
THE DOCTOR
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10
votes
3 answers
OSPF link cost design
What kind of processes and/or tools do you use to design OSPF cost on links in your environments?
harrijs
- 136
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10
votes
1 answer
Cisco IOS Forward / reverse name lookups
I want to configure our Ciscos so they can do forward DNS resolution, but not reverse DNS resolution from the CLI.
R01(config)#ip domain-name domain.local
R01(config)#ip name-server 10.1.1.1
R01(config)#ip domain-lookup
That config makes the router…
user2339
- 105
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10
votes
1 answer
Long login delay when cisco device is booted
Whenever we boot or reboot a Cisco router or switch we have to wait a number of minutes before we can get a username prompt for login. We get a few fail messages
Press RETURN to get started.
% Authentication failed
% Authentication failed
%…
Adam Loveless
- 3,129
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10
votes
3 answers
Selecting IPv6 Unique Local Addresses (ie, choosing least-sig 40 bits)
We started with fec0::/10 for site-local addresses -- but that is now deprecated. Instead, we now have fc00::/7 reserved, with fd00::/8 dedicated to /48 nets for Unique Local Addresses.
What's the best practice for picking the least-sig 40 bits to…
Craig Constantine
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10
votes
4 answers
What OSI layer do Access Points operate on?
I am studying for CCNA. In my book I read that wireless access points belong to OSI layer 2. I did some research and I found that is correct. This raised lots of questions in my head so I hope I don't get on your nerves :P
I know that these devices…
BrunoMCBraga
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10
votes
1 answer
Cisco IOS: Show ip route output order
I am runing some BGP tests through the lab before rolling them out in production (thus, any IP addresses or AS numbers etc used here are done so in a completely fictitious manner).
Something that has always bugged me is the output on Cisco IOS of…
Baldrick
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