In previous illustration, find the equivalent resistance of the network between 1 and 2.

Explanation

From symmetry, it si clear the current in
resistors connected between points (1 and 8) and (1 and 4)
should be same hecne points 4 and 8 are equipotential points.
Similarly, the current in resistor connected between points
(2 and 7) and (2 and 3) should be same, hence points 3 and 7
are equipotential points.
We can join points (4 and 8) and (3 and 7). we can redraw
the cirucit and calculate the equivalent resistance as shown in
fig. 5.128