OSPF peers with same router ID
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Hi Herediano, Route flapping occurs if Route-ID is the same in the same area.
R1 and R2, R2 and R3 can all establish neighbors normally, and there will be problems when synchronizing the database. In R2's LSDB, there is only one copy of LSA (LSA1 and LSA2) with adv of 1.1.1.1, and routing calculation problems will occur. Assume that R1 advertises the route 10.10.10.0/24. R1 sends the LSA (adv=1.1.1.1type=1, LS ID=1.1.1.1, seq=80000001) to R2. After receiving the LSA, R2 sends it to its neighbor R3. After receiving the LSA, R3 finds that the advertiser is 1.1.1.1, but does not have the network segment, then, R3 sends an LSA1 (age=1s, seq=80000002) to R2. After receiving the LSA1, R2 compares it with the LSA with the adv=1.1.1.1, selects the LSA1 with a larger sequence number, and forwards the LSA1 to R1. After receiving the LSA1, R1 finds that it has the network segment, a new LSA1 (seq=80000003) is sent. Such a repetitive situation may occur, causing route flapping. Assume that R1 imports a route to 10.10.10.0/24. R1 sends the LSA (adv=1.1.1.1, type=5, LS ID=1.1.1.1, seq=80000001) to R2. After receiving the LSA, R2 sends it to R3. After receiving the LSA, R3 finds that the advertiser is 1.1.1.1, but does not have the network segment, then, R3 sends an LSA5 (age=3600s, seq=80000001) to R2. After receiving the LSA5, R2 compares it with the LSA5 received previously. Because the seq and checksum are the same as those before, R2 preferentially selects the LSA5 with age=3600s, then, R1 forwards the LSA5 to R1. After receiving the LSA5, R1 finds that it has the network segment and sends a new LSA5 (seq=80000002). Such a repetitive situation may occur, causing route flapping. I hope it helps! |
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Hi Herediano, Route flapping occurs if Route-ID is the same in the same area.
R1 and R2, R2 and R3 can all establish neighbors normally, and there will be problems when synchronizing the database. In R2's LSDB, there is only one copy of LSA (LSA1 and LSA2) with adv of 1.1.1.1, and routing calculation problems will occur. Assume that R1 advertises the route 10.10.10.0/24. R1 sends the LSA (adv=1.1.1.1type=1, LS ID=1.1.1.1, seq=80000001) to R2. After receiving the LSA, R2 sends it to its neighbor R3. After receiving the LSA, R3 finds that the advertiser is 1.1.1.1, but does not have the network segment, then, R3 sends an LSA1 (age=1s, seq=80000002) to R2. After receiving the LSA1, R2 compares it with the LSA with the adv=1.1.1.1, selects the LSA1 with a larger sequence number, and forwards the LSA1 to R1. After receiving the LSA1, R1 finds that it has the network segment, a new LSA1 (seq=80000003) is sent. Such a repetitive situation may occur, causing route flapping. Assume that R1 imports a route to 10.10.10.0/24. R1 sends the LSA (adv=1.1.1.1, type=5, LS ID=1.1.1.1, seq=80000001) to R2. After receiving the LSA, R2 sends it to R3. After receiving the LSA, R3 finds that the advertiser is 1.1.1.1, but does not have the network segment, then, R3 sends an LSA5 (age=3600s, seq=80000001) to R2. After receiving the LSA5, R2 compares it with the LSA5 received previously. Because the seq and checksum are the same as those before, R2 preferentially selects the LSA5 with age=3600s, then, R1 forwards the LSA5 to R1. After receiving the LSA5, R1 finds that it has the network segment and sends a new LSA5 (seq=80000002). Such a repetitive situation may occur, causing route flapping. I hope it helps! |
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