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الموضوع: ISL vs 802.1q

  1. #1
    عضو
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    ISL vs 802.1q



    Alsalam 3alikom:
    I have a question to ask:
    If I have in my switched internetwork a Catalyst 2950 series which support 802.1Q encapsulation connected with
    a trunk link to Catalyst 1900 which support ISL encapsulation only,is that mean that I can't connect
    them with a VLAN environment(cause the two ends of the trunk should have the same encapsulation)?
    or there is a method to have a VTP messaging between the two switches.
    Thank you in advanse.

  2. #2
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    Post مشاركة: ISL vs 802.1q

    اقتباس المشاركة الأصلية كتبت بواسطة ahmedtea
    Alsalam 3alikom:
    I have a question to ask:
    If I have in my switched internetwork a Catalyst 2950 series which support 802.1Q encapsulation connected with
    a trunk link to Catalyst 1900 which support ISL encapsulation only,is that mean that I can't connect
    them with a VLAN environment(cause the two ends of the trunk should have the same encapsulation)?
    or there is a method to have a VTP messaging between the two switches.
    Thank you in advanse.
    Al salam alikom,,,

    Yes, you can connect both switches of two different encapsulation method -ISL & dot1q- to have a communication between different Vlans. But, why??
    ok, becoz when you want to have a communication between different Vlans on your two different cat. switches (1900 & 2950), you will need a layer3 device -could be a router- to maintain the rounting process, and here the encapsulation will takes place and,moreover, you will need to configure two different encapsulation types for both switches on the layer3 device.

    But, what if i only want to communicate with same Vlans on different types of switches??
    Here, there s no need for encapsulation to be specified on both switches.! oh.! why??
    bcoz, of the TRUNK. i.e, what you will do is to configure turnk ports on both switches and then, it will work.! agine why?they are different switches models???
    bcoz, when trunk takes place, by default it will pass frames of even differ types of switches for both directions i.e, for those two different switches. The only one thing you need to do here is to specify and configure which ports will be your trunk ports on both switches. Thats all.

    Any comments will be welcomed & negotiated.

    Thank You..
    --------------------------------------------------------
    B.Sc (Hon) Computer Eng

    CCNA

  3. #3
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    مشاركة: ISL vs 802.1q

    Brother Kidman
    Shortly u mean that when we configure port in Catalyst 1900 with ISL & method
    &
    at the other side in the 2950 we will configure the port with 802.1q trunk method
    here the trunk will work between the 2 switches
    ????????????????????????????????????????????

    Allah Bless All

  4. #4
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    مشاركة: ISL vs 802.1q

    Alsalam 3alikom:
    Mr.Kidman,As I know that you must have the same encapsulation type on both side of the trunk to do negotiation between the two tunk port on the two switches.
    thx

  5. #5
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    Post مشاركة: ISL vs 802.1q

    اقتباس المشاركة الأصلية كتبت بواسطة F_A_H_D
    Brother Kidman
    Shortly u mean that when we configure port in Catalyst 1900 with ISL & method
    &
    at the other side in the 2950 we will configure the port with 802.1q trunk method
    here the trunk will work between the 2 switches
    ????????????????????????????????????????????

    Allah Bless All
    Al salam Alikom...........

    No, i didnt mean that.!, Here what i mean :

    why do we need to configure (ISL and dot1q)?
    Acually, we need to configure it when we want to have a communication between different VLANS, on different types of switches -say 1900 and 2950-.

    Where should we configure the (ISL or dot1q) encapsulation??
    we sould configure those types of encapsulation on a layer3 device, ok ok, on a router. but NOT on switches.

    fine, then what to configure in the switches??
    we should configure a TRUNK port/s between switches on both same or different type. a Trunk does NOT need to be specified if its a (ISL or dot1q), because by default it can pass through both types of encapsulations, thats why.

    Any other things r welcomed, and negotiated..
    --------------------------------------------------------
    B.Sc (Hon) Computer Eng

    CCNA

  6. #6
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    مشاركة: ISL vs 802.1q

    اقتباس المشاركة الأصلية كتبت بواسطة KiDmAn
    ...........



    fine, then what to configure in the switches??
    we should configure a TRUNK port/s between switches on both same or different type. a Trunk does NOT need to be specified if its a (ISL or dot1q), because by default it can pass through both types of encapsulations, thats why.

    Any other things r welcomed, and negotiated..
    on Catalyst 2950 series the only encapsulation type is 802.1q.
    on catalyst 1900 series the only encapsulation type is ISL.
    so on both series you can't specified which type of encapsulation you want.
    but as an example on Catalyst 3550 series "the 3550 can run both ISL and the IEEE 802.1Q trunking
    encapsulation method—the 2950 can only run 802.1Q" from SYBEX 5th edition
    so if you connect a 3550 with either 1900 or 2950 you shouldn't do any configuration on the trunk.
    and cause ISL is a cisco proprietary SYBEX 5th edition said "IEEE 802.1Q
    Created by the IEEE as a standard method of frame tagging, it actually inserts
    a field into the frame to identify the VLAN. If you’re trunking between a Cisco switched link
    and a different brand of switch, you have to use 802.1Q for the trunk to work"
    I hope that my idea is clear.

  7. #7
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    Post مشاركة: ISL vs 802.1q

    اقتباس المشاركة الأصلية كتبت بواسطة ahmedtea
    on Catalyst 2950 series the only encapsulation type is 802.1q.
    on catalyst 1900 series the only encapsulation type is ISL.
    so on both series you can't specified which type of encapsulation you want.
    but as an example on Catalyst 3550 series "the 3550 can run both ISL and the IEEE 802.1Q trunking
    encapsulation method—the 2950 can only run 802.1Q" from SYBEX 5th edition
    so if you connect a 3550 with either 1900 or 2950 you shouldn't do any configuration on the trunk.
    and cause ISL is a cisco proprietary SYBEX 5th edition said "IEEE 802.1Q
    Created by the IEEE as a standard method of frame tagging, it actually inserts
    a field into the frame to identify the VLAN. If you’re trunking between a Cisco switched link
    and a different brand of switch, you have to use 802.1Q for the trunk to work"
    I hope that my idea is clear.
    Thank you for declaration, but:

    I guess you are repeating what i was said.!, I said we do not need to configure an encapsulation on switch when trunking-even if they are of a different models- because TRUNK by default will pass all types of encapsulation between switches.

    Anything is welcomed.
    --------------------------------------------------------
    B.Sc (Hon) Computer Eng

    CCNA

  8. #8
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    مشاركة: ISL vs 802.1q

    بعد السلام
    الاخوه الكرام
    اذا عاوزين توصيل بين isl & dotq1
    حنحتاج ل راوتر 3550 لانه الوحيد البدعم ال isl & dotq1 في نفس الوقت
    اما 2500 فهو يدعم فقط isl
    و 2600 يدعم dotq1
    الاوامر في 3550 كالاتي
    conf#switchport trunk encapsulation isl
    or
    conf#switchport trunk encapsulation dotq1

    ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++
    reply in english
    dear brother's
    only 3350 can support both isl and dotql
    so we have to use it in our network
    and the configuration will be like
    conf#switchport trunk encapsulation isl
    or
    conf#switchport trunk encapsulation dotq1

  9. #9
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    مشاركة: ISL vs 802.1q

    ya gama3aaaaaaaaaaaaaaa
    Brother
    i didnt got what u mean
    if i have 2 switches 1900 & 2950
    i can make trunk link between them or not
    ???????????????????????????????????????
    if yes
    HoW
    ????
    (without 3550)
    THNX

  10. #10
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    Post مشاركة: ISL vs 802.1q

    اقتباس المشاركة الأصلية كتبت بواسطة F_A_H_D
    ya gama3aaaaaaaaaaaaaaa
    Brother
    i didnt got what u mean
    if i have 2 switches 1900 & 2950
    i can make trunk link between them or not
    ???????????????????????????????????????
    if yes
    HoW
    ????
    (without 3550)
    THNX
    Al salam Alikom

    The answer is : YES of course, you can make a TRUNK between them.

    HOW??: ok here, below an example of simple configuration showing the asnwer:
    Suppose you have 2 switches (1900 &2950), each switch connect to one PC. Both PCs are in the same VLAN say learn. And we need to TRUNK them, because we need to exchange some info. -frames- from PC1 to PC2, knowing that two PCs are agin on different switches models (one on 1900 and the other on 2950).

    ok. what to do next??
    Let us start with the 1900 switch:

    sw1900# conf t
    sw1900(config)# ip address 192.168.1.1 255.255.255.0 <-- assigning ip addr. for management purposes. We can also assign an ip default-gateway addr., if we need to route info -frames- of different VLANs accross a router..
    sw1900(config)# vlan 10 name learn <-- creating a VLAN 10
    sw1900(config)# int e0/1
    sw1900(config)#vlan-membership static 10 <-- assiging PC1 to the VLAN 10
    sw1900(config)#exit <-- To here we created a Vlan called (learn) and we assigned PC1 which is connected to (e0/1) on 1900 to this Vlan.

    Now, let us move to the second switch (2950), and do the same:
    sw2950(config)# int vlan 1
    sw2950(config-if)# ip address 192.168.1.2 255.255.255.0 <--assigning ip addr. for management purposes. We can also assign an ip default-gateway addr., if we need to route info -frames- of different VLANs accross a router..
    sw2950(config-if)# no shut
    sw2950(config-if)# exit
    sw2950(config)# exit
    sw2950# vlan database

    sw2950(vlan)# vlan 10 name learn <-- creating the same VLAN 10 as 1900 switch
    sw2950(vlan)#exit
    sw2950# conf t
    sw2950(config)#

    sw2950(config-if)# int f0/1 <-- PC2 is connected to this port of 2950.
    sw2950(config-if)# switchport access vlan 10 <-- assiging PC2 to VLAN 10
    sw2950(config-if)# exit
    To the pervious step, everthing s ok. Each switch has one PC, both PCs are belongs to same VLAN, but on different switches as well as different switche's types.

    Now, we want to communicate between those 2 PCs, what to do??
    yes, thats right. We need to configure a TRUNK which will do the job for us.!. Remember switches are of different models.

    How to configure a Trunk??

    Trunk on 1900:
    sw1900(config)# int f0/27 <-- this s the port on which i choose to trunk 1900 to 2950, you can choose any port, but make sure its a (Fastethernet NOT Ethernet).
    sw1900(config-if)# trunk on <-- trunk command
    sw1900(config-if)# exit
    till here, the joke s end with 1900 switch. We can notice that we didnt define any encapsulation method while trunking to 2950.

    Trunk on 2950:
    sw2950(config)# int f0/12 <-- chosen port for trunking to 1900, you can choose any other port, all ports on 2950 are Fastethernet ports.
    sw2950(config-if)# switchport mode trunk <-- trunk command
    sw2950(config-if)# exit

    Now, we finished configuration on both switches without any talk about encapsulation method used.

    * Hint: i didnt give any ip addr. to PCs, u can assign addrs for them, to use ping command.

    How can we know if its working????

    Ping s king.!

    I hope that i explain it clearly.

    Thank U..
    --------------------------------------------------------
    B.Sc (Hon) Computer Eng

    CCNA

  11. #11
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    مشاركة: ISL vs 802.1q

    الاخ kidman شكرا للمجهود بارك اللة فيك
    بس انت مش جايب سيرة VTP Modes or VTP Domain
    !!!!!!!!

  12. #12
    عضو الصورة الرمزية ramixpe
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    مشاركة: ISL vs 802.1q

    Alsalam 3lykom
    shortlyyyyyyyyyyyyyyy
    you cant without a router!!!!!1
    and when you think about the router it become a INTERVLAN sul.......

  13. #13
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    مشاركة: ISL vs 802.1q



    اقتباس المشاركة الأصلية كتبت بواسطة esaesa
    يا جماعة لو ال encabsulation مختلف موش ممكن يحصل إتصال
    This is the idea which I believed.
    "both switch ports must be configured for trunking, and they must both be configured with the same tagging mechanism (ISL or 802.1Q"
    Refrence: http://www.ciscopress.com/articles/a...&seqNum=3&rl=1

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