Friday 7 March 2014

CCDP - ARCH - Well Known Multicast Addresses

In the CCDP ARCH exam there are numerous refereences to Multicast addresses.

This post is to simply catalogue those that are specifically refered to in the various reading materials I've covered.

Address Scope:

  • /4 - Class D reservation

Address type:

  • to - assigned by IANA for services (detailed below)
  • to - Control Block - assigned by IANA for traffic crossing public networks e.g.- NTP
  • to - AD-HOC block assigned by IANA for addresses that don't fit the above ranges
  • to - AD-HOC block assigned by IANA for addresses that don't fit the above ranges
  • to  AD-HOC block assigned by IANA for addresses that don't fit the above ranges
  • - Source-Specfic Multicast Addresses
  • - GLOP addresses - Originally experimental now publically assigned addresses for use by ISPs and any organisation want to ublich content over Multicast
  • - Uni-cast Prefix addresses
  • - Administratively scoped IPv4 addresses, locally assigned, not globally unique
Well Known Addresses:

  • The All Hosts multicast group addresses all hosts on the same network segment.
  • The All Routers multicast group addresses all routers on the same network segment.
  • The Open Shortest Path First (OSPF) All OSPF Routers address is used to send Hello packets to all OSPF routers on a network segment.
  • The OSPF All Designated Routers ""(DR)"" address is used to send OSPF routing information to designated routers on a network segment.
  • The Routing Information Protocol (RIP) version 2 group address is used to send routing information to all RIP2-aware routers on a network segment.
  • The Enhanced Interior Gateway Routing Protocol (EIGRP) group address is used to send routing information to all EIGRP routers on a network segment.
  • Protocol Independent Multicast (PIM) Version 2
  • Virtual Router Redundancy Protocol (VRRP)
  • - 21 IS-IS over IP
  • Internet Group Management Protocol (IGMP) version 3
  • Hot Standby Router Protocol version 2 (HSRPv2) / Gateway Load Balancing Protocol (GLBP)
  • Network Time Protocol clients listen on this address for protocol messages when operating in multicast mode.
  • The Cisco multicast router AUTO-RP-ANNOUNCE address is used by RP mapping agents to listen for candidate announcements.
  • The Cisco multicast router AUTO-RP-DISCOVERY address is the destination address for messages from the RP mapping agent to discover candidates.
  • H.323 Gatekeeper discovery address
  • Simple Service Discovery Protocol address

  • Saturday 4 December 2010

    For a while now I've been a little unsettled at using the domain particularly after Jeremy Cioara's experience of looking down the business end of Cisco's legal department.

    So, I've moved. From now on my study notes, thoughts, and helpful hints will be located at :o)

    Cisco - Catch me if you can!

    See you there...

    Thursday 2 December 2010

    New home for Jeremy Cioara...

    Where is Jeremy?...

    I'm busy tidying things up before I start my series of notes on CCNP Switch and I thought I'd check in with Jeremy, so I go to his ammended blog and low and behold I'm redirected to

    It's been a while since I last took a look at what the Master had to say so I'll be spending some time here over the next few days seeing what's what.

    Keep up the good work Jeremey :o)

    Tuesday 26 October 2010

    Subnet Mask vs Wildcard Mask

    Something I find I struggle with is when to use a subnet mask and when to use a wildcard mask. This article is to simply set out the instances when you will use one or the other (not the actual steps to apply them).

    Subnet Mask:

    • When applying an IP to an interface
    • Routing protocol summary addresses
    • BGP
    • PIX security appliance ACL's
    • ASA security appliance ACL's
    • When creating DHCP pools on a Switch or Router

    Wildcard Mask:
    • EIGRP network statements
    • OSPF network statements
    • VPN concentrator network lists (when setting the local and remote allowed networks)
    • Router ACL's
    This list is not exhaustive and I will add to it as I come across new instances where you use either a Subnet mask or Wildcard mask. 

    Friday 17 September 2010

    BSCI Exam - Passed!

    Well, I've just got back from the test centre and I'm pleased to say that I passed!!

    It was a bit touch and go though as I think there was about 1 minute 30 seconds left on the clock.

    No rest though as I've already started CCNP SWITCH at my local Cisco Networking Academy.

    As you'll guess, most posts from now on will be SWITCH related.


    Wednesday 15 September 2010

    BSCI - OSPF - Adjacency requirements

    For an OSPF adjacency to form the 2 neighbors must agree on several parameters within the Hello Packet before the adjacency can form. These are:

    i) Each must have a unique Route-ID
    ii) Each must be in the same Area
    iii) Authentication setting must match
    iv) Timers must match.

    One other parameter that must be agreed upon is the router priority for DR/DBR elections.

    BSCI - Manipulating Routing Updates - Route-map permissions

    When compiling a Route-map(RM), you set an access control list (ACL) then use the Route-map to match addresses set out in that ACL to apply your chosen criteria in the Set field of the Route-map.

    Now the question is given the combination of permit or deny statements in the ACL and the permit or deny statement of the Route-map what is the out come for a packet.

    The following is what happens to a given packet when the permit or deny statements are considered:

    ACL = Permit
    RM= Permit
    Result = Packet Permitted to proceed via the route-map. That's to say the packet is permitted to be permitted.

    ACL = Deny
    RM = Permit
    Result = Packet Denied. The packet is denied from being permitted.

    ACL = Permit
    RM = Deny
    Result = Packet Denied. The packet is permitted to be denied.

    ACL = Deny
    RM = Deny
    Result = Packet PERMITTED. The packet is denied from being denied. If it isn't allowed to be denied, it must, therefore, be permitted.

    Bit of a weird one to get your head round but it's an obvious trick to chuck in there when you're under pressure so keep an eye out.

    Tuesday 14 September 2010

    BSCI - IPv6 - IP address types

    The following is a list of IPv6 address types. The high order bits are displayed and their function:

    i) 001 = Global - 200
    ii) 1111 1111 = Multicast - FF
    iii) 1111 1110 11 = Site Local - FEC0
    iv) 1111 1110 10 = Link Local - FE80
    v) ::X:X:X:X = IPv4 compatible address, where the first 96 bits are set to 0 (hence the ::) and the remaining 32 bits are converted to hex from the IPv4 address

    Other addresses include:
    ::1 or 0:0:0:0:0:0:0:1 = Loopback
    ::/128 = unspecified address which is essentially the DFG for IPv6, all the bits are set to 0.
    IPv6 private addresses start - 1111 1110 1 - therefore both site local and link local are private

    BSCI - EIGRP - Adjacency Requirements

    The following criteria need to be meet before an EIGRP adjacency will form:
    i) Authentication (if in place)
    ii) AS Number
    iii) Source IP MUST be the primary address for the interface - secondary IP's will not result in the adjacency forming
    iv) K values must match

    N.B. - Timers do not have to match but they must be equal.
    - Adjacency will flap if timers are mismatched.
    - Therefore ensure you have a reliable time source.

    BSCI - ISIS - Adjacency requirements

    For an ISIS adjacency to come up the following criteria must match:
    i) MTU  - default is 1497
    ii) Router Levels - L1, L1/L2, L2 only
    iii) If L1 router, the IS must be in the same area
    iv) System ID's must be unique
    v) Authentication (if used)

    Adjacency is formed after a 3-way handshake. The stages are DOWN - INIT- UP

    The adjacency is up if the neighbor has put you identity in their hello packet.