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  1. #1
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    Question 8 IPs (5 useable) what are the other 3 for?

    I see many hosts promiss 8 IPs (5 useable). But why don't they just say 5 IPs? What are the other 3 IPs for? Viewable from within VLAN, but not from outside, like a NAT system?

  2. #2
    As I understand it, the host assigns a small block of 8 addresses. 3 are needed to properly setup a network: 1 is used for a router address, 1 for a network address and 1 for subnet broadcast.

  3. #3
    or, they could be reserved for an HSRP configuration. HSRP (Hot Standby Router Protocol) is a way to introduce another layer of redundancy. See: http://www.cisco.com/univercd/cc/td/.../ics/cs009.htm
    Dan - Vice President - [email protected]
    BurstNET Technologies - http://www.burst.net

  4. #4
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    In a /29 private VLan you have 8 IPs used and 5 that can be utilized for actual servers.. Here's how they break down..


    192.168.1.0 Network Address
    192.168.1.1 Gateway Address
    192.168.1.2 Usable IP
    192.168.1.3 Usable IP
    192.168.1.4 Usable IP
    192.168.1.5 Usable IP
    192.168.1.6 Usable IP
    192.168.1.7 Broadcast Address



    Edited because I hit tab too fast...
    James Lumby

  5. #5
    I see many hosts promiss 8 IPs (5 useable). But why don't they just say 5 IPs?
    Well, it is probably to satisfy the curiosity of those technie customers.

  6. #6
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    "Well, it is probably to satisfy the curiosity of those technie customers."

    More like "we are using 8, these 8 are your vlan, but you can only use 5" if you've been around long enough it makes sense. **thinks back of the days of shared /24's

  7. #7
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    Well, it is probably to satisfy the curiosity of those technie customers.
    Or have an explanation why they are charging you $8 for a second batch of 5 IPs.

  8. #8
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    Originally posted by rotoiti
    Or have an explanation why they are charging you $8 for a second batch of 5 IPs.
    Because they don't like to plan with additional space, or have the headache of expanding it.

    If you know you are going to need more ip's... request they assign you a /28 instead of a /29 when you sign up. It'll still cost you your $8 extra dollars, but you'll get all 8 ip's that your paying extra for, usable.
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  9. #9
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    They can just add 8 ips to your vlan when you need it...
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  10. #10
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    Anyone knows if rc.conf is the only thing I need to bring the extra 4 IPs other than the 1 main ip up?

    Currently I have in rc.conf
    ifconfig_fxp0="inet xxx.xx.xxx.102 netmask 255.255.255.248"
    defaultrouter="xxx.xx.xxx.101"

    Ok, so the software router is at 101, and main ip is 102, what more lines I need to add?

  11. #11

  12. #12
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    Originally posted by The Broadband Man
    They can just add 8 ips to your vlan when you need it...
    Well you can't really add IP's to a vlan, (ie expand the vlan) as it's likely IP's infront of and behind your block have been allocated, you'd probably be assigned either an additional vlan, or a brand new bigger block.

    I've actually been experimenting with routing individual IP's as /32's (which saves a lot of address space), and it does appear to work quite nicely.

    Dan

  13. #13
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    Originally posted by burstdan
    or, they could be reserved for an HSRP configuration. HSRP (Hot Standby Router Protocol) is a way to introduce another layer of redundancy. See: http://www.cisco.com/univercd/cc/td/.../ics/cs009.htm
    How do you setup HSRP and still get 5 usable IP's in your VLAN?

    HSRP by any configuration I know will yield 3 usable IP's, and 5 "consumed" by the network.

  14. #14
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    Originally posted by RazorBlue - Dan
    Well you can't really add IP's to a vlan, (ie expand the vlan) as it's likely IP's infront of and behind your block have been allocated, you'd probably be assigned either an additional vlan, or a brand new bigger block.

    I've actually been experimenting with routing individual IP's as /32's (which saves a lot of address space), and it does appear to work quite nicely.

    Dan
    Sure you can, you just take another block and slap them into the vlan.

    Granted, it's not as pretty as one big block... but nobody cares about pretty any more... which shows, as your routing /32's
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  15. #15
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    yeah definitely - expand the vlan and add more ips ... not that big of a deal
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  16. #16
    Originally posted by porcupine
    How do you setup HSRP and still get 5 usable IP's in your VLAN?

    HSRP by any configuration I know will yield 3 usable IP's, and 5 "consumed" by the network.
    Depends on the subnet. We deal mainly with /28s, so that gives us 5 usable. It also, of course, depends on the number of routers that you want to make part of the whole show....
    Dan - Vice President - [email protected]
    BurstNET Technologies - http://www.burst.net

  17. #17
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    Originally posted by burstdan
    Depends on the subnet. We deal mainly with /28s, so that gives us 5 usable. It also, of course, depends on the number of routers that you want to make part of the whole show....
    Out of 16 IP's you have 11 go to the network? , what possible purpose would that serve? 1N+7?

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