January 7, 2010
I had a interesting question from a friend today.
Assume the following scenario:
Im going to exclude any MPLS connectivity, as it is not relevant.
The PE (Router1) connects the CE (Router3) with two links, one serial and one wireless.
This particular ISP runs mostly static routes to client sites (within the VRF’s) or alternatively eBGP.
On a wireless link it is always good practise to run BGP to detect when connectivity with the remote end is lost in the underlying Layer2 network. (Preventing a blackhole)
Regarding routing on the Serial Link, there as a default route out from Router 3 and a static route to 10.33.33.0/24 on Router1 pointing to Router3.
The client wants to load-balance traffic across both links. And the Admin Distance of the static route was set to 20 to match eBGP. (this is the scenario)
So the question : Why does Router1 not install both routes (the eBGP route and the Static), both with an prefix-length of /24, a Admin Distance of 20, and metric of 0 into the RIB??
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Posted in General info | Tagged Routing | 1 Comment »
January 7, 2010
Inspired by the flow chart that Mr Richard Bannister did for the BGP route path selection, I did one for conventional route-selection in the RIB.
Posted in General info | Tagged Routing | 1 Comment »
December 24, 2009
Often knowing the necessary show commands is not enough, you need to understand the output.
Here is a good example and breakdown of each of the fields with the command:
show traffic-shape
VC = 'DLCI's'
Access List = 'Used to shape traffic of common type for separation'
Target Rate = 'CIR in bits'
Byte-Limit = 'Bc+Be ie the size the token bucket, express in BYTES'
Sustain bits/int = 'Bc value per Tc, (int is short for interval or Tc)'
Excess bits/int = 'Be value'
Interval (ms) = 'Tc value'
Increment (bytes) = 'How many bytes of token replenished each Tc, ie Bc value in bytes'
Adapt Active = 'Shows Adaptive shaping has been enabled. If a BECN is received, the flow is throttled back'
What else can be set about the configuration here?
The interface have 3 DLCI’s defined.
DLCI’s 413 and 405 have a CIR of 56k. This was not configured. This is default behaviour. When ‘frame-relay traffic-shaping’ is enabled each DLCI on that interface will be allocated a 56k CIR unless changed. Here it is clear that DLCI 403 has a map-class policy applied.
Oh and Merry Christmas guys 
Posted in Frame-Relay, OUTPUT-101, QOS | Tagged FRTS, OUTPUT-101 | Leave a Comment »
December 21, 2009
While searching for CCIE jokes, I found an old forum thread at Cisco Learning network containing jokes about the man, the legend, the hex-translator, the missing E-bit(evil) : Scott Morris.
Here are some of the jokes I think is pretty funny:
- Scott Morris once planned a cross-country trip using a Route Map!
- Scott Morris plays a rather unique instrument called the ISAKMP!
- Every VPN is an EasyVPN for Scott Morris!
- When Scott Morris was four years old he was putting together OSI models!
- Scott Morris’ home wireless network runs on brain waves!
- Scott Morris slayed the Kerberos daemon.
- Scott Morris’s driver’s license is a PDF!
- If you doubt Scott Morris just sh Scott | s certification
- There are no hidden IOS commands. Only those Scott Morris chooses not to look at!
- Scott Morris has counted to pi.. twice!
- Normal people teach their dogs to fetch. Scott Morris taught his dog to route.
- Morpheus was searching for Scott Morris!
- Scott Morris doesn’t have a steering wheel in his car. He has a CLI!
- Scott Morris found Waldo in an extended access control list!
- Scott Morris is actually an undercover SNMP Agent!
My favourite three are :
- Scott Morris ran track in high school and always won the 100 meter frame relay!
- He taught his dog to ARP! arp, arp, arp, arp.
- MD5 : Morris Digests 5 CCIE’s for breakfast!
Posted in Humour | Leave a Comment »
December 17, 2009
This chapter provides perfect insight about the concise content of each technology section covered in Short-Notes V4.
Short-Notes is the definitive CCIE R&S Study guide.
Feel free to download, but please let me know you views and comments : blog@ru.co.za . Alternative please rate this post (click on title, then rate below). 
OSPF Short-Notes
Posted in OSPF | Tagged CCIE R&S, CCIE Study Guide, OSPF | 3 Comments »
December 15, 2009
Serialization/Access-Rate is the physical clocking speed of the interface (ie 64-kbps/128-kbps etc), which determines the amount of data that can be encapsulated on to the wire.
Serialization Delay or Serialization Rate is a constant based on the access rate of the interface. It is the time needed to place data on the physical wire.
These values are set in hardware and cannot be changed.
A data frame can be sent onto the physical wire ONLY at the serialization rate of the interface. Thus serialization delay is the size of the frame in bits divided by the clocking speed of the interface.
Serialization Delay = Frame Size/Link Speed
For example, a 1500-byte frame (12000-bites/64000-bites) will take 187.5ms to serialize (put on the wire) on a 64-kbps circuit.
|
Link- |
Frame Size (Bytes) |
|
Speed |
64 |
128 |
256 |
512 |
1024 |
1500 |
|
64 kbps |
8 ms |
16 ms |
32 ms |
64 ms |
128 ms |
187 ms |
|
128 kbps |
4 ms |
8 ms |
16 ms |
32 ms |
64 ms |
93 ms |
|
256 kbps |
2 ms |
4 ms |
8 ms |
16 ms |
32 ms |
46 ms |
|
512 kbps |
1 ms |
2 ms |
4 ms |
8 ms |
16 ms |
23 ms |
|
768 kbps |
0.640 ms |
1.28 ms |
2.56 ms |
5.12 ms |
10.4 ms |
15 ms |
For low-speed WAN connections (those with a clocking speed of 768kbps or below), it might be necessary to provide a mechanism for Link Fragmentation and Interleaving (LFI) when running delay sensitive application like voice.
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Posted in QOS | Tagged LFI, QOS | Leave a Comment »
December 10, 2009
This chapter provides perfect insight about the concise content of each technology section covered in Short-Notes V4.
Short-Notes is the definitive CCIE R&S Study guide.
Feel free to download, but please let me know you views and comments : blog@ru.co.za . Alternative please rate this post (click on title, then rate below).
Switching Short-Notes
Posted in Switching | Tagged CCIE R&S, CCIE Study Guide, Switching | 2 Comments »
December 3, 2009
This chapter provides perfect insight about the concise content of each technology section covered in Short-Notes V4.
Short-Notes is the definitive CCIE R&S Study guide.
This IPv6 Study Guide additionally includes :
- RIPng
- EIGRP for IPv6
- MPBGP
- IPv6 Multicast
Even though it is unlikely that RIPng and MPBGP would be asked, it might be. Regardless of that, you not only studying to be a CCIE, you also studying to become an elite network engineer. This is why it is covered. No holes and no shortcuts!
Feel free to download, but please let me know you views and comments : blog@ru.co.za. Alternative please rate this post (click on title, then rate below).
IPv6 Short-Notes
Posted in IPv6 | Tagged CCIE R&S, CCIE Study Guide, IPv6 | Leave a Comment »
December 2, 2009
Had really annoying problem yesterday. Was busy setting up Role-Based TACACS access on Cisco ACS and happily configuring the NDG (Network Device groups), the Command Authorization Sets etc.
Started testing and kept on getting “% Authentication failed” on the CLI.
At first you realize you must have made a typo or forgot to do something. Double check the config, the ACS setup and confirm the passwords are correct with no Null Spaces. But still no luck.
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Posted in Security | Tagged Cisco ACS | Leave a Comment »
November 26, 2009
When BGP peers set up their session between them, they send an OPEN message containing optional parameters.
One optional parameter is capabilities. Possible capabilities are Multiprotocol extensions, route refresh, outbound route filtering (ORF), and so on. When the BGP peers exchange the Multiprotocol extension capability, they exchange AFI and SAFI numbers and thus identify what the other BGP speaker is capable of.
IPv6 in BGP is implementated via Multi-Protocol BGP (MPBGP) (RFC 2283), as is MPLS and VPN’s through two new attributes: MP_UNREACH_NLRI and MP_REACH_NLRI. The first two values in these two attributes contain the Address Family Identifier (AFI) and the Subsequent Address Family Identifier (SAFI).
| AFI |
Meaning |
| 1 |
IPv4 |
| 2 |
IPv6 |
.
| SAFI |
Meaning |
| 1 |
Unicast |
| 2 |
Multicast |
| 3 |
Unicast and multicast |
| 4 |
MPLS Label |
| 128 |
MPLS-labeled VPN |
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Posted in BGP, OUTPUT-101 | Tagged BGP, OUTPUT-101 | Leave a Comment »
November 19, 2009
I really enjoy meeting and discovering the people who helped build, engineer and nurture the industry I love so much. Also, those key individuals that have seen and helped the networking industry to grow to the colossal size it is today. I admire these individuals as they give me perspective on my achievements and more importantly, motivate me to follow in their steps. This is why the CCIE was my first stop.
Emmanuel Conde (aka Eman) from CCIE Flyer, has been involved in IT since before networking and the CCIE program came about. Eman is very well-known by those people who matter in the Networking Realm.
During his travels he has met some of the most influential individuals, who I would like to meet one day. From Scott Morris to Terry Slatery to Darby Weaver, they all know Eman and talk highly of him. He is also the only CCIE recruiter promoted by Cisco Systems. But what is so incredible about Eman, is that he tirelessly devotes most of his time to developing Cisco talent, and placing CCIE candidates from all over the world in their deserving jobs. His believe and support in the networking industry is truly inspiring.
So what? Why the fuss? Well Eman, is the man who knows the trades and trends, I think better than most. Eman has a publication that reaches thousands of people every month, called the CCIE Flyer. It contains the latest news and happenings regarding CISCO, the CCIE Program and other general Networking stuff. I read through most of the content, which is really appetising.
Feel free to visit Eman’s site and subscribe to it:)
Posted in Non Tech stuff, Resources | Leave a Comment »
November 11, 2009
A good friend of mine has just passed his 3rd CCIE, and to my knowledge, this makes him the ONLY tripple CCIE in South-Africa.
He was one of the first security CCIE in Africa in 2003, and now James has earned himself the elite position of being 1 of 390 people in the world… holding 3 CCIE’s.
Huge congratulations and well done!!!
Posted in Non Tech stuff | Leave a Comment »
November 10, 2009
I often see guys still using windows calculator to do Hex 2 Binary 2 Decimal conversions for Port numbers, Protocol numbers, DSCP values etc…
I have been using a small utility for years and have not yet come across a better one.
It was written by Live Bat Programming Group, I can’t find an official website only an email address : dagus2@geocities.com (not sure if it is still valid).
It is called HEXBINDEC (descriptive I know):
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Posted in General info | Leave a Comment »
November 9, 2009
Everybody knows how to use the include|begin|exclude search operators (I hope so at least), but you can also search through config with the “/” operator. You can use this with almost any SHOW command that is more than one page long. Although similar to linux and useful it is only half as good.
I use this mostly when I want to see the configuration following a specific search string bound to show up multiple times from the SHOW command.
Example: Show the running-config, and one the first page break, hit the forward slash “/”. Now enter the string you looking for:
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Posted in General info | Leave a Comment »
November 2, 2009
It is never nice when devices on a network go belly-up, but to know why or what happened right before they went belly-up, is crucial.
By enabling CPU and Memory thresholding, you can be sure to get those vital notifications when it happen allowing you to respond a lot quicker.
When a router is overloaded by processes, the amount of available memory might fall to levels insufficient for it to issue critical notifications, so the first step is to reserve some memory:
memory reserve critical {kilobytes}
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Posted in General info | Leave a Comment »
